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Physiologically Based Dissolution Testing in a Drug Development Process—a Case Study of a Successful Application in a Bioequivalence Study of Trazodone ER Formulations Under Fed Conditions

  • Poznan University of Medical Sciences, Faculty of Pharmacy

Abstract and Figures

Development of generic extended-release (ER) formulations is challenging. Especially under fed conditions, the risk of failure in bioequivalence trials is high because of long gastric residence times and susceptibility to food effects. We describe the development of a generic trazodone ER formulation that was aided with a biorelevant dissolution evaluation. Trazodone hydrochloride 300-mg monolithic matrix tablets were dissolved both in USP and EMA compliant conditions and in the StressTest device that simulated both physicochemical and mechanical conditions of the gastrointestinal passage. The final formulation was tested against the originator, Trittico XR 300 mg, in a randomized cross-over bioequivalence trial with 44 healthy volunteers, in agreement with EMA guidelines. Initially developed formulations dissolved trazodone similarly to the originator under standard conditions (f2 factor above 50), but their dissolution kinetics differed significantly in the biorelevant tests. The formulation was optimized by the addition of low-viscosity hypromellose and mannitol. The final formulation was approved for the bioequivalence trial. Calculated Cmax were 1.92 ± 0.77 and 1.92 ± 0.63 [μg/mL], AUC0-t were 27.46 ± 8.39 and 29.96 ± 9.09 [μg∙h/mL], and AUC0-∞ were 28.22 ± 8.91 and 30.82 ± 9.41 [μg∙h/mL] for the originator and test formulations, respectively. The 90% confidence intervals of all primary pharmacokinetic parameters fell within the 80–125% range. In summary, biorelevant dissolution tests supported successful development of a generic trazodone ER formulation pharmaceutically equivalent with the originator under fed conditions. Employment of biorelevant dissolution tests may decrease the risk of failure in bioequivalence trials of ER formulations.
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Research Article
Physiologically Based Dissolution Testing in a Drug Development Processa
Case Study of a Successful Application in a Bioequivalence Study of Trazodone
ER Formulations Under Fed Conditions
Dorota Danielak,
Bartłomiej Milanowski,
Krzysztof Wentowski,
Maria Nogowska,
Piotr Rogowski,
Łukasz Konwicki,
Ewa Puk,
Jarosław Pieczuro,
Marek Bawiec,
Grzegorz Garbacz,
and Janina Lulek
Received 26 November 2019; accepted 13 March 2020
Abstract. Development of generic extended-release (ER) formulations is challenging.
Especially under fed conditions, the risk of failure in bioequivalence trials is high because of
long gastric residence times and susceptibility to food effects. We describe the development
of a generic trazodone ER formulation that was aided with a biorelevant dissolution
evaluation. Trazodone hydrochloride 300-mg monolithic matrix tablets were dissolved both
in USP and EMA compliant conditions and in the StressTest device that simulated both
physicochemical and mechanical conditions of the gastrointestinal passage. The nal
formulation was tested against the originator, Trittico XR 300 mg, in a randomized cross-
over bioequivalence trial with 44 healthy volunteers, in agreement with EMA guidelines.
Initially developed formulations dissolved trazodone similarly to the originator under
standard conditions (f
factor above 50), but their dissolution kinetics differed signicantly
in the biorelevant tests. The formulation was optimized by the addition of low-viscosity
hypromellose and mannitol. The nal formulation was approved for the bioequivalence trial.
Calculated C
were 1.92 ± 0.77 and 1.92 ± 0.63 [μg/mL], AUC
were 27.46 ± 8.39 and
29.96 ± 9.09 [μgh/mL], and AUC
were 28.22 ± 8.91 and 30.82 ± 9.41 [μgh/mL] for the
originator and test formulations, respectively. The 90% condence intervals of all primary
pharmacokinetic parameters fell within the 80125% range. In summary, biorelevant
dissolution tests supported successful development of a generic trazodone ER formulation
pharmaceutically equivalent with the originator under fed conditions. Employment of
biorelevant dissolution tests may decrease the risk of failure in bioequivalence trials of ER
KEY WORDS: Trazodone; Generic; Bioequivalence; Extended release; Biorelevant dissolution.
The global pharmaceutical market requires high-quality
generic drugs. Solely in the USA, approximately 90% of
prescribed drugs are generic; at the same time, they account for
less than a quarter of total expenses on prescription drugs (1). In
2018, savings from generic drug prescription amounted to 292.6
billion dollars in the USA alone (2). Pharmaceutical companies
are required to prove bioequivalence of the manufactured generic
drug with a brand name product unless the regulatory agency
approves biowaiver. This process is time- and cost-consuming.
Therefore, the sponsor of the study should make all the efforts to
develop a formulation that will ensure the success of the
pharmacokinetic bioequivalence trial. Drug pharmacokinetics
differs both within and between subjects due to physiological
conditions such as sex, age, or genetic polymorphisms of enzymes
involved in the metabolism of xenobiotics. Therefore, variability of
Electronic supplementary material The online version of this article
( contains supplementary
material, which is available to authorized users.
Department of Physical Pharmacy and Pharmacokinetics, Faculty of
Pharmacy, Poznan University of Medical Sciences, 6 Święcickiego st,
60-781, Poznań, Poland.
Department of Pharmaceutical Technology, Faculty of Pharmacy,
Poznan University of Medical Sciences, 6 Grunwaldzka st, 60-780,
Poznań, Poland.
Biofarm Sp. z o.o, 13 Wałbrzyska st, 60-198, Poznań, Poland.
Institute of Computer Engineering, Control and Robotics, Wroclaw
University of Technology, 27 Wybrzeże Wyspańskiego st, 50-370,
Wrocław, Poland.
Physiolution GmbH, Walther-Rathenau Strasse 49a, 17489,
Greifswald, Germany.
To whom correspondence should be addressed. (email:
AAPS PharmSciTech (2020) 21:161
DOI: 10.1208/s12249-020-01662-8
1530-9932/20/0000-0001/0 #2020 The Author(s)
drug dissolution should be as low as possible. Also, drug release
from generic formulation should resemble the brand name
product as closely as possible under fasted and fed conditions, if
applicable. It is even more critical in modied (MR) and extended-
release (ER) formulations. As the ER forms are designed to
release the active ingredient over prolonged time, they are prone
to food effects (3). Koziolek et al.(3) distinguished three categories
of food effects relevant for MR and ER dosage forms: (i) drug-
related factors including partition coefcient, stability in different
pH values, or absorption rate; (ii) formulation-related factors
comprising dose, size, excipients, and drug release proles; and (iii)
physiology-related factors including gastrointestinal motility, spe-
cicpHprole, gastric emptying, or food composition and caloric
content. Novel test methods allow the in vitro evaluation of drug
dissolution proles under physiologically relevant conditions.
They allow the use of media simulating the composition of uids
in human gastrointestinal tract, such as simulated gastric uid
(SGF)orsimulatedintestinaluid (SIF) (4). Additionally, devices
such as Dissolution Stress Test (5)oraFedStomachModel(6)can
effectively simulate shear stresses generated by peristaltics during
gastrointestinal passage. As shown in the SmartPill® studies, these
contractions generate pressure up to 500 mbar, especially in the
antro-pyloric region during gastric emptying (7).
Since the drug delivery of ER products is often
dependent on their geometry, the simulation of mechanical
stresses in dissolution tests, such as simulated motility forces
or dynamic events of transport, can effectively point dissim-
ilarities between ER formulations under biorelevant condi-
tions (8). Different susceptibility of formulations to
mechanical stress in vivo can cause irregular drug release
and increase pharmacokinetic variability (9,10). Therefore,
advanced dissolution stress devices can aid the successful
development of high-quality generic drugs.
In this paper, we demonstrate the development of a
generic trazodone ER formulation. Trazodone is a weak base.
This Biopharmaceutics Classication System (BCS) Class II
drug is sparingly soluble in water, and its experimentally
evaluated logP is 2.9 (11). It is also pH sensitive with a pK
about 6.74 (12). Trazodone is most commonly used as a salt of
hydrochloric acid.
The novelty of the study is an intensive use of bio-
predictive, physiology-mimicking dissolution tests during the
formulation development process, leading to a successful
bioequivalence trial under fed conditions. Until now, the
usefulness of the StressTest device was used for the develop-
ment of novel, pressure-sensitive dosage forms (13) or for an
explanation of observed uctuations in the pharmacokinetics
of drugs administered as ER formulations (10). Therefore,
the paper presents a new application of the device for
bioequivalent generic drug development.
Trazodone Formulations
Generic trazodone hydrochloride ER tablets (Trazodon
XR 300 mg), containing 300 mg of the active ingredient
(equivalent to 273.2 mg of trazodone), were manufactured by
a direct compression method. The dissolution proles of the
active substance were tested along with the brand name
productTrittico XR 300 mg (Aziende Chimiche Riunite
Angelini Francesco A.C.R.A.F. S.p.A.). Six batches, labeled
A to F, were tested in biorelevant conditions. The qualitative
composition of each analyzed batch is available in Table I.
The amount of the active ingredienttrazodonedid not
exceed 35% of total tablet mass.
Dissolution Media
In the development process, both standard and
biorelevant media were used. Standard media included
0.1 M hydrochloric acid with 2.92 g/L sodium chloride
(pH 01.2) and 50 mM phosphate buffer pH 06.0. Biorelevant
media were 50 mM phosphate buffer at pH ranging from 4.5
down to 1.8 (with the addition of HCl), and 50 mM phosphate
buffer pH 06.5 with FaSSIF (Fasted State Simulated Intesti-
nal Fluid)/FeSSIF (Fed State Simulated Intestinal Fluid)/
FaSSGF (Fasted State Simulated Gastric Fluid) powder
( Ltd., London, UK) in a concentration
corresponding to a fed state. All of the reagents were of
analytical grade.
Dissolution Tests
Each tablet batch was preliminarily tested in a standard
dissolution media. Then, it was investigated further in
biorelevant conditions resembling fed state. In all biorelevant
tests, the dissolution proles of trazodone from generic
formulations were compared with the originator. If the
dissolution prole differed signicantly from the originator,
reformulation and further characterization were performed.
The batch with the dissolution prole most comparable with
the brand name product was qualied for use in the clinical
bioequivalence trial.
Standard Dissolution Tests
Standard dissolution tests were performed in a conven-
tional USP dissolution apparatus 2 (Agilent VK7025 and
Agilent 708 DS) with a constant paddle rotation at 150 rpm,
according to Guideline on quality of oral modied release
productsissued by European Medicines Agency (EMA)
(14). The tablets were placed in USP compliant Japanese
basket sinkers. The conditions used for dissolution studies
were based on a Trazodone once daily patent documentation,
No. US7829120B2 (12). Initially, the dissolution medium was
0.1 M hydrochloric acid with 2.92 g/L sodium chloride (pH 0
1.2). After 1 h, the medium was exchanged to a 50-mM
phosphate buffer pH 06.0. Dissolution proles were deter-
mined for 24 h. Collected samples were assayed with a high-
performance liquid chromatography method, validated ac-
cording to Validation of Analytical Procedures: Text and
Methodologyguidelines developed by the ICH (15). The
chromatographic separation was performed on an XBridge
C18 column 3.5 μm, 75 × 4.6 mm (Waters, MA, USA), using
acetonitrile and triuoroacetic acid (0.2%) (35:65; v/v) as a
mobile phase, at the isocratic ow rate of 1.2 mL/min. The
total run time was 2 min, the injection volume was 5.0 μL, and
the detection (UV-Vis) wavelength was set at 246 nm. The
column temperature was maintained at 25°C. Additionally, an
161 Page 2 of 11 Danielak et al. (2020) 21:161
similarity factor was calculated, according to the EMA
guideline (16). The f
values greater than 50 ensured the
equivalence of both test and originator products in standard
dissolution studies.
Biorelevant Dissolution Tests
Stress Test Device. The dissolution stress test device was
rst introduced by G. Garbacz and W. Wetschies (9). The
core principle of the StressTest device is to simulate the
mechanical agitation of physiological intensity that acts on a
solid dosage form during the GI transit as well as the
physicochemical conditions in the subsequent sections of the
GI. A detailed description of the device is given elsewhere
Test Setup Parameters. Dissolution tests were designed
to simulate the fed intake conditions of the bioequivalence
trial. First, the medium was 1100 mL 50 mM phosphate buffer
at pH 4.5. The pH of the medium was gradually decreased to
1.8 by addition of 5 M hydrochloric acid; then, after 5 h the
pH was adjusted to pH 6.5 by the addition of 40% sodium
hydroxide, and 40 mL of a FaSSIF/FeSSIF/FaSSGF concen-
trate solution in a 50 mM phosphate buffer concentrate was
added (77.9 g of the powder in a 50 mM phosphate buffer,
lled up to a nal volume of 240 mL, stirred until dissolved,
and allowed to settle for at least 1 h before addition to the
media). The nal concentration of the FaSSIF/FeSSIF/
FaSSGF in the simulated intestinal uid was 11.2 g/L,
corresponding to the fed state. The media change pattern
was aligned with the simulation of the mechanical aspects of
the GI tract. The stress program was set up. Figure 1presents
stress as well as the media type and change pattern used in
the present biorelevant dissolution studies.
Determination of Trazodone in Biorelevant Media. The
amount of the drug dissolved was determined every 10 min
using online closed-loop UV-Vis spectroscopy. The samples
were ltered through a PES (polysulfone) lter with a pore
size of 1 μm (Sartorious, Göttingen, Germany) and analyzed
in a ow-through mode. Flow-through quartz cuvettes of a 5-
mm path length (Hellma, Müllheim, Germany) were used
with an Agilent 8543 spectrophotometric system (Agilent,
Santa Clara, USA) with the photometers set to a differential
mode at two wavelengths of λ0313 nm for trazodone signal
and λ0450 nm for the background, respectively.
Bioequivalence Study
The bioequivalence study was a single-center, single-
dose, open-label (laboratory blinded), randomized, four-
period, four-way cross-over study, according to the Guide-
line on the pharmacokinetic and clinical evaluation of
modied release dosage forms(EMA/CPMP/EWP/280/96
Corr1) (17). The protocol of the study was approved by the
Independent Ethics Committee at the Regional Chamber of
Physicians in Warsaw, and by the Ofce for Registration of
Medicinal Products, Medical Devices and Biocidal Products
in Poland. The trial was registered in the EU Clinical Trial
Register under the number 2018-000598-57.
Sustained and predictable release of the drug from the
ER dosage is more challenging in fed conditions than in a
fasted state, both in dissolution studies and in the proper
setup of the clinical study protocol. Therefore, in this paper,
we will present the results of the bioequivalence trial
performed under fed conditions only.
Study Group
The minimum sample size needed to adequately assess
the bioequivalence of two trazodone formulations was
calculated as suggested by Diletti et al.(18). Based on the
reported clinical studies NCT00839072 (19)and
NCT01121900 (20), the C
of trazodone after administra-
tion of 300 mg trazodone hydrochloride varies intra-
individually by approximately 29%. Assuming the power of
the test at 80% and signicance level α00.05, the bioequiv-
alence assessment required at least 38 subjects.
The study included forty-four healthy subjects of both
sexes. The characteristics of the study group are presented in
Table II. Each subject signed an Informed Consent Form.
Before and during the study, the subjects had to refrain from
the use of other drugs, products containing nicotine, alcohol,
caffeine, or grapefruit juice. Each subject had the right to
withdraw from the study. The participation of a subject might
have been discontinued for reasons including adverse events
and study protocol deviation.
Table I. Composition of Developed Formulations Tested in Biorelevant Dissolution Tests. For All of the Ingredients Besides Trazodone
Hydrochloride, the Values Are Presented as Mass Percentages of the Total Mass of the Tablet
Ingredient A B C D E F
Trazodone hydrochloride (mg) 300
Hypromellose 100,000 (%) 1619 2124 2124 510 510 510
Hypromellose 4000 (%) –––510 510 510
Microcrystalline cellulose (%) 2025 2025 1520 2332 2026 2026
Silicied microcrystalline cellulose (%) 2025 1520 1520 1619 1619 1619
Mannitol (%) ––383636
Talc (% 12
Magnesium stearate (%) 12
Polyvinyl coating Yes Yes Yes No No Yes
161 Page 3 of 11Dissolution Tests in Generic Drug Development (2020) 21:161
A single dose of the test product (Trazodon XR 300 mg)
or the brand name product (Trittico XR 300 mg), both
containing 300 mg trazodone hydrochloride, was adminis-
tered by the oral route. The administration was within 30 min
after the start of a standardized high-fat meal, with 250 mL of
still, room temperature water. No other uid intake was
allowed from 2 h before until 1-h post-dosing. Additionally,
uids were administered as follows: 250 mL of uid with
breakfast, 150 mL of still water at 1, 2, and 3 h post-
administration, 200 mL uid with meals at 4 and 12 h post-
administration, and 100 mL at 5, 6, 7, 8, 9, 10, and 11 h post-
administration. Standardized lunch and supper were served at
about 4 and 12 h after drug administration.
From each subject 4 mL of full blood was collected
before drug administration (time 0), and at 1, 2, 3, 4, 5, 6, 8,
9, 10, 11, 12, 13, 14, 15, 16, 20, 24, 28, 32, 36, 42, 48, and 72 h
after the intake of the drug. The blood samples were taken
before the intake of uids. Full blood was collected through
heparinized capillaries into a vacuum blood collection system.
Immediately after collection, the samples were centrifuged,
and the plasma was transferred into separate tubes, stored in
dry ice, and shipped into the laboratory for trazodone
determination. Any deviations from the sampling protocol
were noted, and the actual sampling times were reported for
further analysis.
Determination of Trazodone Concentrations and
Pharmacokinetic Parameter Calculations
Plasma samples were shipped in dry ice to an external,
certied laboratory for the determination of trazodone. The
drug concentrations were determined with a high-
performance liquid chromatography mass spectrometry
method (LC-MS), in a multiple reaction monitoring mode
(MRM). The method was validated according to the EMA
guidelines in terms of selectivity, accuracy, and precision (21).
The lower limit of trazodone quantitation was 10 ng/mL.
The pharmacokinetic evaluation was planned in agree-
ment with the guideline CPMP/EWP/QWP/1401/98 Rev.
1/Corr** (16) and EMA/CPMP/EWP/280/96 Corr1 (17).
Following pharmacokinetic parameters were considered for
bioequivalence evaluation: area under the time-concentration
curve from time 0 to 72 h (AUC
), area under time-
concentration curve extrapolated to innity (AUC
), and
maximum concentration obtained directly from the measured
concentrations (C
). Additional secondary parameters
included time to C
) and plasma half-life (T
) that
was calculated from 0.693/K
represents the
elimination rate constant determined through a linear regres-
sion. Of note, only the actual sampling times were used. The
parameters were calculated by the linear-log trapezoidal rule
in Phoenix WinNonlin software, build (Certara
USA, Princeton, NJ, USA).
Bioequivalence after a single dose of trazodone 300 mg
under fed conditions was established upon a ratio of test and
reference product parameters. Before the analysis, the
parameters were log-transformed. The 90% condence
interval for the ratio should be contained within 80.00
125.00%. The pharmacokinetic parameters were analyzed
with ANOVA test, with factors for sequence, subject within
sequence, period, and treatment. Also, the Schuirmanns two
one-sided parametric T tests were calculated with the null
hypothesis of bioinequivalence at the 5% (α00.05) level of
Standard Dissolution Tests
The release proles of trazodone from tested formula-
tions are presented in Fig. 2. All of the tablets release the
active substance steadily over 24 h. Most of the formulations
released less than 30% of trazodone within the rst hour, no
less than 70% after 12 h, and at least 80% after 24 h from the
beginning of the dissolution study. The originator released
trazodone slower than any of the tested formulations. Batches
A, B, and C resembled most the release prole of the
Fig. 1. Setup of the program for biorelevant dissolution tests
Table II. Characteristics of the Study Group. Data Are Presented as
Means ± Standard Deviations
Parameter Female (n011) Male (n033)
Age (years) 39.3 ± 11.4 33.4 ± 9.3
Weight (kg) 66.0 ± 7.4 74.5 ± 8.3
Body mass index (kg/m
) 23.8 ± 2.8 23.4 ± 2.1
161 Page 4 of 11 Danielak et al. (2020) 21:161
originator. In contrast, batches D, and E released the active
ingredient at a noticeably faster rate. This observation also
holds for the nal batch F that was the model for the clinical
batch. The calculated f
factors were as follows: batch A 0
51.4, batch B 072.3, batch C 069.0, batch D 032.9, batch E 0
33.8, batch F 044.3.
Dissolution Tests in Biorelevant Conditions
First developed batchesA, B, and Cresembled the
trazodone release prole of the originator during the rst 5 h
(Fig. 3). However, the drug release changed noticeably after
the introduction of 300 mbar stress mimicking the gastric
emptying and transition from gastric to intestinal media. The
mechanical stress affected the dissolution of the originator
more than all of the tested batches. Susceptibility of the
originator to the events of the mechanical stress of
biorelevant fortitude caused a faster release of trazodone
and the complete dissolution of tablet matrices. At the same
time, the generic matrices resisted biorelevant mechanical
agitation and were deformed only slightly. Therefore, further
reformulation was required.
Batches D and E were more similar to the brand name
product. The nal batch F, that was approved for use in the
clinical trial, was developed upon batch E. The only
difference between batches E and F was a polyvinyl coating
that did not inuence the release of trazodone from the
tablets, as shown in Fig. 3. Batch D was not chosen for further
studies because of distinctly different dissolution characteris-
tics under fasted conditions. However, the characterization of
drug release under fasted conditions is outside of the scope of
this paper.
Clinical Bioequivalence Trial
Thirty-nine subjects completed the study. As stated
above, the trial required a minimum of 38 participants to
assess bioequivalence with a sufcient power. Table III
presents the calculated pharmacokinetic parameters for both
formulations. Both primary and secondary parameters of the
test formulation (Trazodon XR 300 mg) resembled those
calculated for the brand name product (Trittico XR 300 mg).
Pharmacokinetic proles of both formulations were similar
(Fig. 4). Individual pharmacokinetic proles are available in
the Online Supplementary Data le (Supplement 1). The
intra-subject variability for AUC
, and C
11.56%, 10.74%, and 22.18%, respectively. The inter-subject
variability for AUC
was 27.80%,
28.83%, and 28.11%, respectively.
ANOVA test showed that the sequence and period
effects were negligible for all primary parameters. One of
the statistically signicant factors was a joint subject and
sequence effect. These parameters affected all three primary
parameters (p< 0.0001). Also, the type of formulation (test
product or the brand name product) inuenced the exposure
to trazodone, expressed as AUC
, and AUC
and p00.0005, respectively). For C
this effect was not
statistically important (p00.5955).
The results of the bioequivalence assessment presented
in Table IV show that the test product fullled the criteria for
bioequivalence with the brand name product under fed
In the present study, we demonstrate how the use of
biorelevant methods, i.e., the biorelevant stress test device,
supported the development of a generic ER trazodone
formulation. The test protocols were utilized to predict the
drug delivery behavior of the tested formulations. In this
context, the performed study served as a proof-of-concept for
the predictive power of the StressTest device. As a result, the
developed formulation fullled the bioequivalence criteria
under fed conditions.
The successful formulation of a generic ER dosage form
is a complex and challenging process. In general, if the
originator and generic formulations are similar, they should
also have similar dissolution characteristics under every
condition tested. However, the formulation can be considered
as equivalent only if the bioequivalence trial is passed under
the same test conditions (fasted and/or fed) as the originator.
It becomes challenging if the exposure to the drug differs
signicantly between fasted and fed states. This phenomenon
is observed for trazodone. Karhu et al.(22) showed that
pharmacokinetics of a once-daily Trazodone Contramid
300 mg formulation differed signicantly between fasted and
fed conditions. The AUC between these two states was
similar. However, after a high-fat meal, the C
of trazodone
was 86% higher compared with fasted conditions. The C
values falling outside 80125% condence intervals show that
two products are not equivalent.
Consequently, the fed conditions can be considered as
more difcult with respect to the development of generics.
Therefore, the present paper aims at the description of the
product performance under fed conditions. The strict criteria
for primary pharmacokinetic parameters obtained in the
bioequivalence trial result in setting up requirements for the
pharmaceutical development and characterization of oral
medicines in the preclinical stage. Such characterization,
especially when performed with biorelevant methodology,
may reduce the risk of failure and accelerate the development
Adequate reection of luminal conditions requires more
than the compendial media. Food ingredients such as lipids,
proteins and their digestion products act as natural surfac-
tants affecting both the solubility of the active pharmaceutical
ingredient (API), as well as hydration and erosion processes
of MR matrices (7). These components are also present in
biorelevant media, such as simulated gastric uid, fed state
simulated intestinal uid, fasted state simulated intestinal
uid, milk, and nutritional drink. Therefore, these media
should be used to predict the disintegration of ER matrices
(23,24). The type of food also affects the tablet erosion
process. In fed conditions the tablets disintegrate slower in
comparison with the fasting state, and thus drug dissolution in
the stomach is delayed (25,26). For this reason, we adjusted
the study protocol to reect the physico-chemical properties
of gastrointestinal uids more accurately than conventional
dissolution media. The media composition and pH proles
and transit times used in the present study were set according
to Koziolek et al.(27,28).
161 Page 5 of 11Dissolution Tests in Generic Drug Development (2020) 21:161
The drug delivery behavior of monolithic hydrogel
matrix tablets, such as ones developed in this study, may be
remarkably affected by the mechanical and hydrodynamical
agitation. Motility forces produce such stress during the
physiologic events of transport such as gastric emptying, and
ileocaecal and colonic passage (29). In some cases, mechan-
ical agitation results in deformation, fast erosion of the tablets
matrices, and an increase in the drug delivery rate or even
dose dumping (29,30). Such agitation may be more pro-
nounced under fed conditions due to increased motoric
activity and passage times through the highly active proximal
parts of gastrointestinal tract. Thus, in the present study, we
used a test program with differing patterns intended for the
simulation of the fed state (Fig. 1). The arrangement of the
stress program was derived from the in vivo studies per-
formed using telemetric capsules (7,27,31). For the fed state,
moderate 200-mbar intragastric stress events were pro-
grammed within the rst 24 h, followed by the major gastric
emptying stress (300 mbar) at 5 h. Then, after the transition
to intestinalconditions, regular stress of 110 and 200 mbar
was introduced. In summary, the fed conditions proposed in
our study (Fig. 1)reect these in vivo ndings according to
both composition, residence times, and stress patterns.
All of the tested tablets were monolithic hydrophilic
matrix systems. First batches (AC) consisted mainly of high-
viscosity hydroxypropyl methylcellulose (hypromellose,
HPMC). In the dissolution study performed according to
USP, they released the drug steadily, reaching almost 95% of
the dose labeled within 24 h. Subsequent batches, D and E,
were characterized by a noticeably faster drug release than
batches AC. In these two batches, the amount of
Hypromellose 100000 was decreased to less than 10% of the
total tablet mass, and a low viscosity Hypromellose 4000 was
introduced; also, batch E included a small amount of
mannitol. Final batch F, which differed from batch E only
by a presence of polyvinyl coating, had a comparable
dissolution prole. Increased release of the drug was also
achieved by increasing the amount of microcrystalline cellu-
lose. Properties of hypromellose may explain observed
dissolution performance. Of note, all of the batches tested in
the USP apparatus had different dissolution kinetics as
compared with the originator, Trittico XR 300 mg. As
revealed later in the test under biorelevant conditions, the
batches with the dissolution proles that were most similar to
the originator performed worse, especially after the transition
to media simulating intestinal uids.
As shown by Conti et al.(32,33), high-viscosity polymers
release the drug through a diffusion-controlled mechanism, as
expressed by Ficks law, while low viscosity gelling agents
promote erosion of the swollen polymer. Poorly water-soluble
drugs, such as trazodone under the simulated intestinal
conditions, are mostly released through the latter mechanism
(34). Additionally, high molecular viscosity polymers may
decrease the drug release rate (35). Other properties of
hypromellose, such as a higher percentage of
hydroxypropoxy groups or particle size, may increase the
dissolution rates (36,37). Other excipients used for the
preparation of the batches include microcrystalline cellulose
and silicied microcrystalline cellulose. They show good
binding properties, are compatible with a broad range of
drugs, and are physiologically inert; silicied microcrystalline
cellulose also has an increased surface area and improved
ow characteristics (38,39). Lastly, mannitol can also increase
drug release due to the faster uptake of water (40). All of
these excipients contributed to an improved dissolution of
trazodone from the test tablets.
Fig. 2. Trittico XR 300 mg and Trazodon XR 300 mg dissolution proles obtained in standard dissolution tests,
according to USP. Data are presented as means (n04 for Trittico XR 300 mg, AD, n02 for EF) with standard
deviations as whiskers
161 Page 6 of 11 Danielak et al. (2020) 21:161
Interestingly, the dissolution prole of the originator was
characterized by an increased release of the active ingredient
after transition to intestinal media (Fig. 3). None of the
generic products exhibited such a behavior. Trazodone is a
weak base with a pK
06.74, and it is most commonly used as
trazodone hydrochloride. This salt is sparingly soluble in
water, but its solubility increases with an increased acidity of
the media (41). Thus, in the upper gastrointestinal tract,
where pH is below trazodone pK
, it dissolves well. Owing to
the high volume, weak buffering capacity of the dissolution
Fig. 3. Dissolution proles of trazodone from tested Trazodon XR 300 mg batches (AF) versus Trittico XR 300 mg
obtained under simulated fed conditions. Data are presented as means (n06) with standard deviations as whiskers
Table III. The pharmacokinetic parameters calculated from the results obtained in the bioequivalence study under fed conditions for the brand
name product (Trittico XR 300 mg) and the test product (Trazodon XR 300 mg) (n= 39). The data are presented as means ± standard deviations
Parameter C
[μg/mL] AUC
[μgh/mL] AUC
[μgh/mL] T
[h] T
Trittico XR 300 mg 1.92 ± 0.77 27.46 ± 8.39 28.22 ± 8.91 7.46 ± 2.29 9.71 ± 2.75
Trazodon XR 300 mg 1.92 ± 0.63 29.96 ± 9.09 30.82 ± 9.41 7.69 ± 2.07 9.52 ± 3.72
- area under the time-concentration curve extrapolated to innity, AUC
- area under the time-concentration curve between time 0 to
72 hours, C
- maximum concentration, T
- plasma half-life, T
time to maximum concentration
161 Page 7 of 11Dissolution Tests in Generic Drug Development (2020) 21:161
media, and presence of natural surfactants, the solubility of
trazodone is far below the equilibrium solubility. Solubility of
trazodone hydrochloride in the simulated intestinal media
estimated during the course of our experiment (0.15 mg/mL,
data not shown) was much lower than in pure water (18 mg/
mL, (41)). Therefore, the higher release of trazodone from
Trittico XR 300 mg may result from an extensive stress
corresponding to the gastric emptying and it is not an artifact
related to the solubility of trazodone. In the case of solubility
issues, similar tendencies would also be observed for the
generic batches. It underlines a potential advantage of the
Stress Test device to discriminate between stress-susceptible
and robust extended release dosage forms. In contrast with
products developed in the present study, the originator
product relies on granulated cross-linked high-amylose starch
(Contramide®), mixed with hypromellose, anhydrous colloi-
dal silica, and sodium stearyl fumarate (42). Contramide
swells and forms a rubbery gel, similarly to hypromellose
(43), but at the same time it is prone to degradation and
erosion caused by α-amylase (44). Also, the addition of
hypromellose may greatly affect dissolution from cross-linked
amylose-based tablets and cause different pharmacokinetic
proles under fasted and fed conditions, as shown by
Lenaerts et al.(45). The composition of Trittico XR 300 mg
may therefore explain observed differences in the trazodone
bioavailability under fasted and fed conditions and underlines
the importance of biorelevant conditions for a thorough
examination of dissolution proles during product develop-
ment and release of the clinical batches.
The study concluded with a successful clinical bioequiv-
alence trial under fed conditions. A statistically signicant
subject-sequence effect can be explained by a relatively high
intra-subject variability in the studied population. The type of
formulation (the brand name product vs. tested product) was
shown to be signicant for AUC
and AUC
in the latin-
square ANOVA. However, all of the primary pharmacoki-
netic parameters fell within the assumed condence intervals.
Therefore, the formulation effect may be considered as
negligible, and the two formulations may be concluded as
bioequivalent under fed conditions. Besides the development
of a formulation with an optimal release prole, the design of
the study also contributed to the success in the clinical trial.
According to the protocol, not only meals but also uid
intake were tightly scheduled. In the proposed regimen all
subjects received a specic liquid volume every hour after
administration. A recently established consortium in Under-
standing Gastrointestinal Absorption-related Processes
(UNGAP) investigated the food-drug interactions that may
inuence the absorption of orally administered drugs (46).
According to their state-of-art review, the volume of uids
present in the lumen is one of these factors. First, it inuences
the concentration-driven passive uptake of the drug and
saturable membrane transporters, and second, it exerts an
effect on formulation transit times. Another fact is that a
standard breakfast is a high-fat energy-rich meal with a high
fraction of solids. In stomach it creates a layered, heteroge-
neous mass that contains layers of solids, fats and uids (16).
Water, a drink of choice in clinical bioequivalence trials, does
not mix well with gastric contents rich in fats. Instead, it
rapidly follows a so-called stomach road, also known as
Magenstrasse, and is emptied from the stomach. In case of ER
formulations, this may cause even life-threatening conse-
quences due to dose dumping. Also, ad libitum intake of
water during a controlled clinical trial with ER formulations
can lead to a double peakphenomenon and contribute to
the pharmacokinetic variability (47).
Another aspect is tablet residence time and location in
the stomach. If a tablet is taken under fed conditions, it may
remain in a fundus region of the stomach; this part of the
stomach is poorly mixed and acts as storage (48). If the gastric
emptying is delayed, the drug is released slowly and
accumulates in the proximal stomach (48). Then, after the
gastric emptying, it appears in plasma after a long lag phase
and at high concentrations. In consequence it may cause
erratic pharmacokinetic proles and ultimately a failure of
the bioequivalence trial. Proposed frequent drinking schedule
aimed to reduce the risk of drug accumulation in the fundus
and signicantly contributed to the success of the trial.
Fig. 4. Pharmacokinetic proles of Trittico XR 300 mg (originator product) versus Trazodon XR 300 mg (test product).
Data are presented as means with standard deviations as whiskers (n039)
161 Page 8 of 11 Danielak et al. (2020) 21:161
As shown in this study, the development of a pharma-
ceutically equivalent ER dosage form with a BCS II class
active ingredient is a complex process. Simple, compendial
methods may not be adequate to ascertain the success in an
expensive bioequivalence trial. Also, the use of solely
biorelevant media may not be sufcient. In the present study,
tested and reference products differed most signicantly after
the introduction of physiologically relevant stress. Therefore,
we conrmed that for monolithic ER formulations the
gastrointestinal stress could be an essential element of dosage
development. It should be pointed out that all the literature
data available so far, describing the usability of the StressTest
device, concern only its use for prediction of the dissolution
behavior of ER/MR products under fasted conditions.
Consequently, the present manuscript represents an original
work that describes for the rst time the application of the
StressTest device and test protocols capable of predicting the
in vivo drug delivery behavior under the fed state. The
obtained results are supported by the outcome of the clinical
trial being a part of the study.
In summary, the present study shows that a preclinical
development of ER formulations may be aided by advanced
dissolution studies that take into account not only the
composition of luminal uids and respective residence times
but also timing and fortitude of the physiological mechanical
stress that occurs during the gastrointestinal passage.
This publication was developed as a result of industrial
research and development work carried out as part of the
project Implementation of innovative methods for assessing
the release and absorption of drugs in the gastrointestinal
tractNo. RPWP.01.02.00-30-0021/16, co-nanced by the
MarshalsOfce of the Wielkopolska Region within the
Wielkopolska Regional Operational Programme for 2014-
2020 with the support of the European Regional Develop-
ment Fund. D. Danielak is supported in part by the European
Unions Horizon 2020 research and innovation program
under the Marie Skłodowska-Curie grant agreement No
778051 ORBIS - Open Research Biopharmaceutical Intern-
ships Supportand the Ministry of Science and Higher
Education of Poland fund for supporting internationally co-
nanced projects in 2018 to 2022 (agreement No 3899/H2020/
2018/2). This article reects the authorsview only.
Disclaimer Neither the Research Executive Agency nor the Polish
Ministry of Science and Higher Education may be held responsible
for the use which may be made of the information contained
Conict of Interest The authors declare no conict of interest.
Ethics Statement The protocol of the study was approved by the
Independent Ethics Committee at the Regional Chamber of Physi-
cians in Warsaw, and by the Ofce for Registration of Medicinal
Products, Medical Devices and Biocidal Products in Poland.
Open Access This article is licensed under a Creative
Commons Attribution 4.0 International License, which per-
mits use, sharing, adaptation, distribution and reproduction in
any medium or format, as long as you give appropriate credit
to the original author(s) and the source, provide a link to the
Creative Commons licence, and indicate if changes were
made. The images or other third party material in this article
are included in the article's Creative Commons licence, unless
indicated otherwise in a credit line to the material. If material
is not included in the article's Creative Commons licence and
your intended use is not permitted by statutory regulation or
exceeds the permitted use, you will need to obtain permission
directly from the copyright holder. To view a copy of this
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Springer Nature remains neutral with regard to jurisdic-
tional claims in published maps and institutional afliations.
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jurisdictional claims in published maps and institutional afliations.
161 Page 11 of 11Dissolution Tests in Generic Drug Development (2020) 21:161
... Although RCTs are considered the best designs, which rule out bias and the data/results obtained from such clinical research are the most reliable, RCTs may be plagued by miscalculation of the treatment outcomes/bias, problems of cointerventions, and contaminations [48]. ...
Full-text available
Clinical research is an alternative terminology used to describe medical research. Clinical research involves people, and it is generally carried out to evaluate the efficacy of a therapeutic drug, a medical/surgical procedure, or a device as a part of treatment and patient management. Moreover, any research that evaluates the aspects of a disease like the symptoms, risk factors, and pathophysiology, among others may be termed clinical research. However, clinical trials are those studies that assess the potential of a therapeutic drug/device in the management, control, and prevention of disease. In view of the increasing incidences of both communicable and non-communicable diseases, and especially after the effects that Coronavirus Disease-19 (COVID-19) had on public health worldwide, the emphasis on clinical research assumes extremely essential. The knowledge of clinical research will facilitate the discovery of drugs, devices, and vaccines, thereby improving preparedness during public health emergencies. Therefore, in this review, we comprehensively describe the critical elements of clinical research that include clinical trial phases, types, and designs of clinical trials, operations of trial, audit, and management, and ethical concerns.
... Moreover, the amount of mechanical stress the MR formulation especially matrix tablets, are exposed in the GIT, does influence whether the originator and generic formulation are bioequivalent under fasting and fed conditions. Danielak et al. [59] reported the importance biorelevant dissolution testing inclusive of stress modulation, led to the successful development of a pharmaceutically equivalent generic trazodone ER formulation to the originator under fed conditions. Therefore, PBPK models could be very supportive in the formulation development process, if they could capture stress induced dissolution changes in the generic formulations. ...
Full-text available
Physiologically based pharmacokinetic (PBPK) modeling for biopharmaceutics applications holds great promise as modelling and simulation tool in the field of modern oral modified release (MR) products. Understanding of gastro-intestinal absorption related processes is crucial to ensure the successful development of complex oral drug generic products. In the recent years, PBPK approach has been gradually influencing decision making ability of pharmaceutical industry as well as regulatory agencies. However, there is a gap in understanding its contribution in the field of oral modified release products. In this review, we have collected different recent research articles illustrating the significant contribution of PBPK to the research and development process of oral MR products, with special emphasis on generic drug products. Concretely, literature examples on the utility of PBPK formulation development, for in vitro- in vivo correlations (IVIVC) and prediction of oral bioavailability, and for in-silico food effect predictions were included in the review.
... The availability of pressure data from telemetric capsules were highly important as they provided a physiological basis and could be implemented into in vitro tools such as the Dissolution StressTest device, the Gas-troDuo or the tiny-TIM [88,94,95]. In this regard, the application of the Dissolution StressTest device developed by Garbacz and colleagues provided deeper insights into the effect of pressure on drug release from hydrogel matrix tablets and nowadays allows an early evaluation of the robustness of novel drug products towards physiological pressures (Fig. 9) [96,97]. ...
Ingestible sensor systems are unique tools for obtaining physiological data from an undisturbed gastrointestinal tract. Since their dimensions correspond to monolithic oral dosage forms, such as enteric coated tablets or hydrogel matrix tablets, they also allow insights into the physiological conditions experienced by non-disintegrating dosage forms on their way through the gastrointestinal tract. In this work, the different ingestible sensor systems which can be used for this purpose are described and their potential applications as well as difficulties and pitfalls with respect to their use are presented. It is also highlighted how the data on transit times, pH, temperature and pressure as well as the data from different animal models commonly used in drug product development such as dogs and pigs have contributed to a deeper mechanistic understanding of oral drug delivery.
... This is the first study available for the public domain that shows the utilization of the StressTest device to evaluate properties of a dosage form for FIH clinical trials. Until now, the device has been successfully used to evaluate dissolution characteristics of generic SR or delayed-release products [28][29][30][31]. ...
Full-text available
Sustained-release (SR) formulations may appear advantageous in first-in-human (FIH) study of innovative medicines. The newly developed SR matrix tablets require prolonged maintenance of API concentration in plasma and should be reliably assessed for the risk of uncontrolled release of the drug. In the present study, we describe the development of a robust SR matrix tablet with a novel G-protein-coupled receptor 40 (GPR40) agonist for first-in-human studies and introduce a general workflow for the successful development of SR formulations for innovative APIs. The hydrophilic matrix tablets containing the labeled API dose of 5, 30, or 120 mg were evaluated with several methods: standard USP II dissolution, bio-predictive dissolution tests, and the texture and matrix formation analysis. The standard dissolution tests allowed preselection of the prototypes with the targeted dissolution rate, while the subsequent studies in physiologically relevant conditions revealed unwanted and potentially harmful effects, such as dose dumping under an increased mechanical agitation. The developed formulations were exceptionally robust toward the mechanical and physicochemical conditions of the bio-predictive tests and assured a comparable drug delivery rate regardless of the prandial state and dose labeled. In conclusion, the introduced development strategy, when implemented into the development cycle of SR formulations with innovative APIs, may allow not only to reduce the risk of formulation-related failure of phase I clinical trial but also effectively and timely provide safe and reliable medicines for patients in the trial and their further therapy.
Full-text available
Both machine learning and physiologically-based pharmacokinetic models are becoming essential components of the drug development process. Integrating the predictive capabilities of physiologically-based pharmacokinetic (PBPK) models within machine learning (ML) pipelines could offer significant benefits in improving the accuracy and scope of drug screening and evaluation procedures. Here, we describe the development and testing of a self-contained machine learning module capable of faithfully recapitulating summary pharmacokinetic (PK) parameters produced by a full PBPK model, given a set of input drug-specific and regimen-specific information. Because of its widespread use in characterizing the disposition of orally administered drugs, the PBPK model chosen to demonstrate the methodology was an open-source implementation of a state-of-the-art compartmental and transit model called OpenCAT. The model was tested for drug formulations spanning a large range of solubility and absorption characteristics, and was evaluated for concordance against predictions of OpenCAT and relevant experimental data. In general, the values predicted by the ML models were within 20% of those of the PBPK model across the range of drug and formulation properties. However, summary PK parameter predictions from both the ML model and full PBPK model were occasionally poor with respect to those derived from experiments, suggesting deficiencies in the underlying PBPK model.
Biorelevant dissolution tests of oral solid dosage forms open the gate to valid in vitro-in vivo predictions (IVIVP). A recently developed apparatus, PhysioCell, allows mimicking the fluid flow and pressure waves occurring in the human fasted stomach. In this work, we used the PhysioCell to perform IVIVP for vortioxetine immediate-release (IR) tablets: the originator (Brintellix) and generic product candidates (VORTIO). The dissolved drug was monitored in the gastric (StressCell) and intestinal (Collection Vessel) compartments that contained biorelevant media. Simulated intermittent gastric stress at 15 min and 'housekeeping wave' at 30 min increased the dissolution of Brintellix formulations only. A mechanistic model that best described the observations involved the first-order tablet disintegration with a stress-induced enhancement for Brintellix, dissolution of solid particles in the StressCell, and drug transfer to the Collection Vessel. Then, a semi-mechanistic pharmacokinetic model with dissolution parameters as inputs simulated vortioxetine plasma concentrations in healthy volunteers after single and multiple dosing of Brintellix. Despite different dissolution characteristics, VORTIO provided similar concentration profiles to the originator. In conclusion, PhysioCell dissolution tests, combined with semi-mechanistic IVIVP, can be successfully used to develop IR dosage forms exhibiting gastric stress-related effects.
The major aim of oral pharmacotherapy with modified‐release (MR) products is a reliable and reproducible drug release over several hours in order to generate relevant drug plasma concentrations over an extended time period compared to immediate‐release products. In this chapter, the authors guide the reader through the jungle of biorelevant dissolution test methods. They present different approaches to mimic certain aspects of human gastrointestinal (GI) physiology and discuss the pros and cons of the different biorelevant dissolution test methods used to characterize drug release from MR products. The in vivo performance of MR dosage forms is the result of the interplay of various parameters that include the GI physiology of the subject, the pharmacological effects of the drug as well as physicochemical properties of not only the drug but also of the formulation itself.
This chapter aims to demonstrate the value of dissolution within biopharmaceutics and to highlight the types of apparatus used to better understand the mechanisms associated with drug product dissolution and the interplay with gastrointestinal (GI) physiology. Solubility refers to the capacity of solute to dissolve into a solvent and is measured at equilibrium conditions where the maximum solute is dissolved. Convolution is the process of obtaining/predicting a pharmacokinetic profile for a drug from the dissolution data, whilst deconvolution is the opposite that is, extracting the dissolution profile from the pharmacokinetic data. Dissolution apparatus has closely controlled agitation rates either via rotation of the paddle or basket or by controlling the dip rate or fluid flow. Advances based on compendial apparatus and using novel systems have provided biorelevant testing systems to better replicate conditions within the GI tract.
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International organizations have adopted and recognized drug standards, which should be guided by developers in the field of pharmacology. In practice, there is a problem: how to determine whether a reproduced drug sample really satisfies the world standard for its pharmacological action. It is required to implement an algorithm for checking and confirming the bioequivalence of drugs. The purpose of the study is to automate the verification of standards using an appropriate algorithm, i.e. to develop an application for calculating the results of medicinal substances bioequivalence. The methodology is based on the assumption that the identity in the sense of the created effect of the pharmacokinetic curves of the drug concentration in the blood versus time for the test drug and the standard means their therapeutic equivalence. Research methods include Python programming, use of libraries for data visualization; Visual Studio is an application development environment. The desired algorithm and requirements for the developed application are formulated in the results of the study, based on the study of theoretical issues of determining the medicinal substances bioequivalence. Finally, conclusions about the efficiency of the software are made and options for its improvement are proposed.
Physiologically based pharmacokinetic (PBPK) absorption modeling and simulation is increasingly used as a tool in drug product development, not only in support of clinical pharmacology applications (e.g., drug-drug interaction, dose selection) but also from quality perspective, enhancing drug product understanding. This report provides a summary of the status and the application of PBPK absorption modeling and simulation in new drug application (NDA) submissions to the U.S. Food and Drug Administration to support drug product quality (e.g., clinically relevant dissolution specifications, active pharmaceutical ingredient (API) particle size distribution specifications). During the 10 years from 2008 to 2018, a total of 24 NDA submissions included the use of PBPK absorption modeling and simulations for biopharmaceutics-related assessment. In these submissions, PBPK absorption modeling and simulation served as an impactful tool in establishing the relationship of critical quality attributes (CQAs) including formulation variables, specifically in vitro dissolution, to the in vivo performance. This article also summarizes common practices in PBPK approaches and proposes future directions for the use of PBPK absorption modeling and simulation in drug product quality assessment.Graphical abstract
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The simultaneous intake of food and drugs can have a strong impact on drug release, absorption, distribution, metabolism and/or elimination and consequently, on the efficacy and safety of pharmacotherapy. As such, food-drug interactions are one of the main challenges in oral drug administration. Whereas pharmacokinetic (PK) food-drug interactions can have a variety of causes, pharmacodynamic (PD) food-drug interactions occur due to specific pharmacological interactions between a drug and particular drinks or food. In recent years, extensive efforts were made to elucidate the mechanisms that drive pharmacokinetic food-drug interactions. Their occurrence depends mainly on the properties of the drug substance, the formulation and a multitude of physiological factors. Every intake of food or drink changes the physiological conditions in the human gastrointestinal tract. Therefore, a precise understanding of how different foods and drinks affect the processes of drug absorption, distribution, metabolism and/or elimination as well as formulation performance is important in order to be able to predict and avoid such interactions. Furthermore, it must be considered that beverages such as milk, grapefruit juice and alcohol can also lead to specific food-drug interactions. In this regard, the growing use of food supplements and functional food requires urgent attention in oral pharmacotherapy. Recently, a new consortium in Understanding Gastrointestinal Absorption-related Processes (UNGAP) was established through COST, a funding organisation of the European Union supporting translational research across Europe. In this review of the UNGAP Working group “Food-Drug Interface”, the different mechanisms that can lead to pharmacokinetic food-drug interactions are discussed and summarised from different expert perspectives.
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Delivery of orally compromised therapeutic drug molecules to the systemic circulation via buccal route has gained a significant interest in recent past. Bioadhesive polymers play a major role in designing such buccal dosage forms, as they help in adhesion of designed delivery system to mucosal membrane and also prolong release of drug from delivery system. In the present study, HPMC (release retarding polymer) and mannitol (diluent and pore former) were used to prepare bioadhesive and controlled release buccal discs of buspirone hydrochloride (BS) by direct compression method. Compatibility of BS with various excipients used during the study was assessed using DSC and FTIR techniques. Effect of mannitol and HPMC on drug release and bioadhesive strength was studied using a 32 factorial design. The drug release rate from delivery system decreased with increasing levels of HPMC in formulations. However, bioadhesive strength of formulations increased with increasing proportion of HPMC in buccal discs. Increased levels of mannitol resulted in faster rate of drug release and rapid in vitro uptake of water due to the formation of channels in the matrix. Pharmacokinetic studies of designed bioadhesive buccal discs in rabbits demonstrated a 10-fold increase in bioavailability in comparison with oral bioavailability of buspirone reported.
The purpose of this research was to establish an in vitro dissolution testing method to predict the oral pharmacokinetic (PK) profiles and food effects of gabapentin enacarbil formulated as wax matrix extended-release (ER) tablets in humans. We adopted various biorelevant dissolution methods using the United States Pharmacopeia (USP) apparatus 2, 3 and 4 under simulated fasted and fed states. Simulated PK profiles using the convolution approach were compared to published in vivo human PK data. USP apparatus 2 and 4 underestimated the in vivo performance due to slow in vitro dissolution behaviors. In contrast, biorelevant dissolution using USP apparatus 3 coupled with the convolution approach successfully predicted the oral PK profile of gabapentin enacarbil after oral administration of a Regnite® tablet under fasted state. This approach might be useful for predicting the oral PK profiles of other drugs formulated as wax matrix-type ER tablets under fasted state. Graphical Abstract Fullsize Image
Food effects on oral drug bioavailability are a consequence of the complex interplay between drug, formulation and human gastrointestinal (GI) physiology. Accordingly, the prediction of the direction and the extent of food effects is often difficult. With respect to novel formulations, biorelevant in vitro methods can be extremely powerful tools to simulate the effect of food-induced changes on the physiological GI conditions on drug release and absorption. However, the selection of suitable in vitro methods should be based on a thorough understanding not only of human GI physiology but also of the drug and formulation properties. This review focuses on in vitro methods that can be applied to evaluate the effect of food intake on drug release from extended release (ER) products during preclinical formulation development. With the aid of different examples, it will be demonstrated that the combined and targeted use of various biorelevant in vitro methods can be extremely useful for understanding drug release from ER products in the fed state and to be able to forecast formulation-associated risks such as dose dumping in early stages of formulation development.
The Magenstrasse (stomach road) describes the fast emptying of ingested liquids from the postprandial stomach. The occurrence of the Magenstrasse has great importance for drugs administered together with food as it represents a shortcut through the fed stomach and allows rapid onset of plasma levels. In this study, we investigated the effect of different meals, their texture and fat content on the occurrence of the Magenstrasse. Since the administration of water is common 60 min after drug intake in clinical trials, we also investigated the effect of time point of water administration on the Magenstrasse by a second water administration. The texture of solid meals and a higher amount of solid food components turned out to favor the presence of the Magenstrasse. On the other hand, the effect of fat content of the meals was negligible. Additionally, the gastric emptying of water was comparable between the first and the second (60 min later) fluid administration which could lead to an entrainment of drug substance. So far, the Magenstrasse is proven for water, an investigation of other liquid vehicles might be interesting for further mechanistic understanding and utilization. It turned out, that the phenomenon of the Magenstrasse can also occur at later time points in clinical studies and may have great impact on the pharmacokinetic profiles obtained in these studies.
The drug release profile from hydrophilic matrix tablets can be crucially affected by the variability of physicochemical properties of the controlled release agent. This study investigates and seeks to understand the functionality-related characteristics (FRCs) of hydroxypropyl methylcellulose (HPMC) type 2208, K4M grade, that influence the release rate of the model drug carvedilol from hydrophilic matrix tablets during the entire dissolution profile. The following FRCs were examined: particle size distribution, degree of substitution, and viscosity. Eight different HPMC samples were used to create a suitable design space. Multiple linear regression (MLR) and partial least squares regression (PLSR) analysis was used to create models for each time point. The PLSR results show that the first part of the drug release profiles is mainly regulated by the HPMC particle size. Apparent viscosity and hydroxypropoxy content (%HP) become important in later stages of the drug release profile, when the influence of particle size distribution decreases. These findings make it possible to better understand the importance of FRCs. Larger HPMC particles increase drug release in the first part of the drug release profile, whereas decreased apparent viscosity and a higher degree of %HP increase the drug release rate in the later part of the drug release profile.
In the present study temperature, pH and pressure profiles of nine healthy human volunteers were investigated after ingestion of the SmartPill® under conditions simulating the fasted state treatment in bioavailability and bioequivalence studies. In a previously published study the same subjects received the SmartPill® under fed conditions as recommended by the FDA. Since large non-digestible objects are mainly emptied during phase III of the interdigestive migrating motor complex, the gastric residence time of the SmartPill® was found to be clearly shorter under fasting conditions. Intragastric pH values during the initial 5 min were similar with an identical median value of pH 4.6. Interestingly, the median lowest observed intragastric pH value in fasted state was about one pH unit higher than under fed conditions. Highest pressure activity was observed within the stomach, in relation to gastric emptying. In fasted state, pressure values upon gastric emptying varied strongly between 30 mbar and 304 mbar, whereas after fed state ingestion values of at least 240 mbar could always be observed. The data showed highly variable gastrointestinal parameters even under clinical fasting conditions which must be considered when evaluating clinical studies and developing biorelevant in vitro test methods especially for large non-disintegrating dosage forms.
The intraluminal conditions of the fed stomach are critical for drug release fromsolid oral dosage forms and thus, often associatedwith the occurrence of food effects on oral bioavailability. In this study, intragastric pH and pressure profiles present after the ingestion of the high-caloric, high-fat (964 kcal) FDA standard breakfast were investigated in 19 healthy human subjects by using the telemetric SmartPill capsule system (26 13mm). Since the gastric emptying of such large non-digestible objects is typically accomplished by the migrating motor complex phase III activity, the time required for recurrence of fasted state motility determined the gastric emptying time (GET). Following the diet recommendations of the FDA guidance on food effect studies, the mean GET of the telemetric motility capsule was 15.3±4.7 h. Thus, the high caloric value of the standard breakfast impeded gastric emptying before lunch in 18 out of 19 subjects. During its gastric transit, the capsule was exposed to highly dynamic conditions in terms of pH and pressure, which were mainly dependent on further meal and liquid intake, as well as the intragastric capsule deposition behavior.MaximumpH values in the stomach were measured immediately after capsule intake. The median pH value of the 5 min period after capsule ingestion ranged between pH 3.3 and 5.3. Subsequently, the pH decreased relatively constantly and reached minimum values of pH 01 after approximately 4 h. The maximum pressure within the stomach amounted to 293 ± 109 mbar and was clearly higher than the maximum pressure measured at the ileocaecal junction (60 ± 35 mbar). The physiological data on the intraluminal conditions within the fed stomach generated in this study will hopefully contribute to a better understanding of food effects on oral drug product performance.
Gastrointestinal (GI) pH and temperature profiles under fasted-state conditions were investigated in two studies with each 10 healthy human subjects using the IntelliCap® system. This telemetric drug delivery device enabled the determination of gastric emptying time, small bowel transit time, and colon arrival time by significant pH and temperature changes. The study results revealed high variability of GI pH and transit times. The gastric transit of IntelliCap® was characterized by high fluctuations of the pH with mean values ranging from pH 1.7 to pH 4.7. Gastric emptying was observed after 7–202 min (median: 30 min). During small bowel transit, which had a duration of 67–532 min (median: 247 min), pH values increased slightly from pH 5.9–6.3 in proximal parts to pH 7.4–7.8 in distal parts. Colonic pH conditions were characterized by values fluctuating mainly between pH 5 and pH 8. The pH profiles and transit times described in this work are highly relevant for the comprehension of drug delivery of solid oral dosage forms comprising ionizable drugs and excipients with pH-dependent solubility. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci