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Int. J. Pharm. Sci. Rev. Res., 64(2), September - October 2020; Article No. 02, Pages: 8-16 ISSN 0976 – 044X
International Journal of Pharmaceutical Sciences Review and Research
International Journal of Pharmaceutical Sciences Review and Research
Available online at www.globalresearchonline.net
©Copyright protected. Unauthorised republication, reproduction, distribution, dissemina tion and copying of this document in whole or in part is strictly prohibited.
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8
1Asmaa H. Esmaeil*, 1, 2Afaf A. Ramadan,1, 3 Asmaa M. Elbakry
1Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Al-Azhar University (Girls), Cairo, Egypt.
2Department of Pharmaceutics and Pharmaceutical Technology, Faculty of Pharmacy, Egyptian Russian University, Badr City, Egypt.
3Department of Pharmaceutics and Pharmaceutical Technology, Faculty of Pharmacy, Heliopolis University, Cairo, Egypt.
*Corresponding author’s E-mail: asmaaesmaeil@ymail.com
Received: 18-07-2020; Revised: 20-09-2020; Accepted: 26-09-2020; Published on: 20-10-2020.
ABSTRACT
The objective of the present study was to develop and evaluate an oral floating in situ gel of leflunomide (LEF) as liquid gastro-
retentive drug delivery system for treatment of Juvenile Rheumatoid Arthritis (JRA) to improve patient compliance, prolong its gastric
residence time, and reduce the variations of drug concentration in plasma. LEF is a disease modifying anti-rheumatic drug (DMARD)
which effectively reduces the signs and symptoms of active JRA in children and rheumatoid arthritis (RA) in adults. Floating in situ
gelling formulations were prepared using different concentrations of sodium alginate and calcium carbonate. The prepared gels were
characterized for viscosity, drug content, pH, density, in-vitro gelling capacity, floating lag time, floating duration, gelling strength and
in-vitro release study. The formula C4 (containing 1.5% w/v sodium alginate and 1% w/v calcium carbonate) was considered the best
formula since it showed minimum floating lag time (40 sec), optimum viscosity (295.4 cps), and gel strength (45 sec) and has optimum
drug release (98%) for more than 6hr. Therefore, this formula was chosen for further ex-vivo study in rats to detect gel formation in
the stomach. Formula C4 showed good gel formation ex vivo study. Hence, floating in situ gelling system of LEF is considered a novel
approach to increase patient compliance and increase gastric residence time of drug in the stomach, which in turn will maintain its
plasma level.
Keywords: Leflunomide, Juvenile Rheumatoid Arthritis, Floating in Situ Gel, Gastric Residence Time, Gastro-retentive drug delivery.
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DOI:
10.47583/ijpsrr.2020.v64i02.002
DOI link: http://dx.doi.org/10.47583/ijpsrr.2020.v64i02.002
INTRODUCTION
he oral administration route is preferred over the
various other administration routes of drug delivery
due to the many advantages it exhibits. These
advantages include safety, good patient compliance, ease
of ingestion, pain avoidance, and versatility to
accommodate various types of drugs1.
Solid dosage forms may associate with swallowing
problems for geriatric, pediatrics and bedridden patient
and chances of accidental burst release. To solve the
above-mentioned problems, pharmaceutical technologists
have put in their best efforts to develop a Gastro-retentive
liquid dosage forms i.e. in situ gel formulations. The oral
use of liquid pharmaceutical has generally been justified
on the basis of ease of administration to those individuals
who have difficulty swallowing solid dosage forms and
better patient compliance2.
The in-situ gel dosage form is a liquid before
administration but converts into a gel that floats on gastric
contents as it comes in contact with it. It consists of a
solution of low viscosity that on coming in contact with the
gastric fluids, undergoes change in polymeric
conformation, viscous gel having density lower than the
gastric fluids thus floats on the surface of it3.
Gastro-retentive in situ gel forming system provides the
controlled drug delivery within stomach. In situ gel
formation occurs due to one or combination of different
stimuli like pH change, temperature modulation and
solvent exchange4
Formulation of gastro-retentive sol-gel system involves the
use of gelling agent which can form a stable sol system to
contain the dispersed drug and other excipients. The
gelling of this sol system is to be achieved in gastric
environment, triggered by ionic complexation due to the
change in pH. The formulation adopted is a sodium
alginate solution containing calcium carbonate (as a source
of Ca2+) and sodium citrate, which complexes the free Ca2+
ions and releases them only in the acidic environment of
the stomach. The free Ca2+ ions get entrapped in polymeric
chains of sodium alginate thereby causing cross-linking of
polymer chains to form matrix structure. This gelation
involves the formation of double helical junction zones
followed by re-aggregation of the double helical segments
to form a three-dimensional network by complexation
with cations and hydrogen bonding with water5.
Juvenile idiopathic arthritis (JIA) is a chronic autoimmune-
inflammatory disease of unknown etiology. JIA affects up
Development and Characterization of In Situ Gel Containing Leflunomide as a
Gastro-retentive Drug Delivery
T
Research Article
Int. J. Pharm. Sci. Rev. Res., 64(2), September - October 2020; Article No. 02, Pages: 8-16 ISSN 0976 – 044X
International Journal of Pharmaceutical Sciences Review and Research
International Journal of Pharmaceutical Sciences Review and Research
Available online at www.globalresearchonline.net
©Copyright protected. Unauthorised republication, reproduction, distribution, dissemina tion and copying of this document in whole or in part is strictly prohibited.
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9
to 1 to 4 per 1,000 children worldwide and is the most
common cause of autoimmune musculoskeletal disease in
children. Children with JIA have disease onset prior to age
16 years, and present with joint pain, stiffness and swelling
that persists for longer than 6 weeks6.
Leflunomide is an isoxazole derivative, a disease modifying
anti-rheumatic drug (DMARD) which effectively reduces
the signs and symptoms of JRA in children, while inhibiting
joint damage and improving physical function. The
mechanism of action of this drug is mainly owing to the
inhibition of dihydro-orotate dehydrogenase and tyrosine
kinase enzymes7.
LEF is a pro-drug and after oral administration, rapidly
metabolized to its major active form (Teriflunomide) in the
gut wall, plasma and in the liver. It is practically insoluble
in water and is absorbed from gastrointestinal tract at high
rate following the oral administration but undergoes
extensive first pass metabolism. Oral bioavailability of LEF
is 80% for humans8. In order to maintain therapeutic
plasma levels, sustained release (SR) dosage forms may be
beneficial, allowing only one daily administration of the
drug with consequent improvement of patient
compliance. Sustained release drug delivery aimed at
controlling the release rate as well as maintains desired
drug level in the blood which is therapeutically effective
and non-toxic for extended period of time.
MATERIALS AND METHODS
Leflunomide pure sample was kindly supplied by Al Hekma
pharm (Egypt). Sodium alginate was kindly supplied by Al
Kahira Co. (Egypt). Hydrochloric acid, Calcium carbonate
and Sodium citrate were purchased from El-Nasr
pharmaceutical Co. (Egypt).
Drug -polymer compatibility studies
Fourier transform infrared spectroscopy (FTIR)
FTIR Spectra of LEF, sodium alginate and LEF-sodium
alginate physical mixture (1:1w/w) were recorded with an
FTIR spectrometer (Shimadzu, Model-8400 S, Japan) using
potassium bromide disc method. All spectra were
recorded from 400-4000 cm-1 with an empty pellet holder
as reference9.
Differential scanning calorimetry (DSC)
The thermal properties of LEF, sodium alginate and LEF-
sodium alginate physical mixture (1:1w/w) were
investigated using DSC (Shimadzu, Model DSC-50, Japan).
Samples were weighed and encapsulated into flat
bottomed aluminum pans with crimped-on lids. The
scanning speed of 10°C/min from 25°C to 400°C was used
in presence of nitrogen at flow rate of 25 ml/min. A
thermogram is obtained over the temperature range used
with a thermal analyzer equipped with computer soft
program. The instrument was calibrated with pure indium
as reference. Compatibility of materials was identified by
observing any changes occurred in melting points of the
drug10.
Preparation of in situ gel
Floating in situ gel formulations of LEF were prepared using
different concentrations of gelling polymer (sodium
alginate) and complexing agent (CaCO3). In 70ml of
deionized water, various quantities of sodium alginate and
0.25% w/v sodium citrate was dissolved at 60○C using a
heating magnetic stirrer. After cooling to below 40○C, the
weighed amount the drug (400mg), along with various
quantities of calcium carbonate were dispersed uniformly
into the sodium alginate solution with continuous stirring.
The stirring was continued after complete addition until a
uniform dispersion was obtained and the dispersion was
allowed to cool at room temperature. Finally, the volume
was adjusted to 100ml with deionized and the mixture was
mixed well to get the final preparation which was stored in
amber color bottles until further use11.
Selection of working concentration range of gelling
polymer
Various formulations were prepared using sodium alginate
as gelling polymer to select working concentration range
of gelling polymers on basis of in vitro gelling capacity, pH
and pourability (relative viscosity). The rest of ingredients
were not changed12.
Batches "S" were prepared to study the effect of sodium
alginate concentration on physical properties of the in situ
gel as pourability, gel strength, pH, density, swelling index
and gelling capacity. The concentration of sodium alginate
was varied from 0.5, 1, 1.5, 2 and 2.5 % in batches S1 to S5,
respectively as shown in table (1).
Selection of working concentration range of complexing
agent
Various formulations were prepared using calcium
carbonate as complexing agent to select working
concentration range of complexing agent on basis of its
effect on physical properties, floating properties and
release pattern12.
Batches "C" were prepared to study the effect of calcium
carbonate concentration on in-vitro release, the floating
lag time, gel strength, pH, viscosity and the other physical
properties of the in-situ gel. The concentration of calcium
carbonate was varied from 0.25, 0.5, 0.75, 1.0 and 1.5% in
batches of C1 to C5, respectively as shown in table (3).
Weight of sodium citrate (0.25% w/v) was kept constant in
all batches of "S" and "C".
Characterization of LEF in situ gel formulations for
selection of working concentration range of gelling
polymer and complexing agent
All prepared LEF in situ gel formulations were evaluated to
determine physical appearance, pH, drug content, density,
in-vitro gelation and floating studies, viscosity and gel
strength, Also, in-vitro release and kinetic analysis of
release data of LEF from different in situ gel formulations
was determined.
Int. J. Pharm. Sci. Rev. Res., 64(2), September - October 2020; Article No. 02, Pages: 8-16 ISSN 0976 – 044X
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10
Determination of the physical appearance
All the formulations were visually inspected for their
appearance and pourability.
Measurement of the pH
The pH for each of the formulations was measured using a
calibrated pH meter (410A, ORION). The readings were
recorded in triplicate for each formulation and the
averages of the readings were considered13.
Determination of drug content uniformity
Accurately, five milliliters of in situ gel (equivalent to 20 mg
of LEF) was measured and transferred to 1000 ml
volumetric flask. To this 900 ml of 0.1 N HCl was added and
stirred on magnetic stirrer (Thennolyne, Dubuque, U.S.A.)
for 30hr, followed by sonication (UP 400S, Germany) for 15
min. Complete dispersion of contents was ensured visually
and filtered. From this solution, 1 ml of sample was
withdrawn and diluted to 10 ml with 0.1 N HCl. Contents
of LEF were determined spectrophotometrically at λmax 260
nm using UV spectrophotometer (Shimadzu, UV-1601,
Japan). The measurements of drug content were recorded
in triplicate and the average values are calculated14.
Determination of Density
Density of the floating oral in situ gel was determined by
using water displacement method. To (10 ml) in situ
solution, 20 ml of 0.1 N HCl (pH 1.2) was added to convert
the solution into gel. Excess of HCl was drained off and the
gel formed was weighed. The gel was then transferred to a
50 ml measuring cylinder and allowed to settle at the base.
Distilled water was added up to 50 ml marking of
measuring cylinder. Volume of water in the presence of gel
was noted. From the difference in the volumes of water
with and without gel the volume of gel was obtained i.e.
amount of water displaced by the gel was calculated15.
In vitro gelation study
Five milliliters of the simulated gastric fluid (0.1N HCl, pH
1.2) in a 15ml test tube maintained at 37°C followed by the
addition of 1 ml of the formulation using a pipette. The
pipette was positioned facing the surface of the fluid in the
test tube and slowly the formulation was released from the
pipette. When the formulation came in contact with the
gelation medium, it was quickly converted into a gel-like
structure. Based on the stiffness of gel as well as the
duration, for which the gel remains as such, the in-vitro
gelling capacity was investigated16.
The in vitro gelling capacity was mainly divided into three
categories based on immediate gelation time and
extended period, the formed gel remains.
(+) Gels within five min, dispersed within 4 hr
(++) Gels within 60 sec and retains gel structure for up to
8hr.
(+++) Gels immediately and retains gel structure for up to
12 hr.
In vitro floating study
The in vitro floating study was carried out by introducing
10 mL of formulation into a beaker containing 100 ml of
0.1N HCl, (pH 1.2) at 37°C without much disturbance.
The time required for the formulation to emerge on the
medium surface (floating lag time) and the time the
formulation constantly floated on surface of the
dissolution medium (duration of floating) were
recorded17,18.
Measurement of viscosity
Viscosity of the prepared in situ gel was determined by
Brookfield viscometer (Model DV-II, Germany). The
samples (10ml) were sheared at a rate of 50 rpm/min using
spindle number 2 at room temperature. Viscosity
measurement of each sample was done in triplicate, each
measurement taking approximately 30 sec19.
Measurement of gel strength
A sample of 50g of the gel formed in 0.1 N HCl (pH 1.2) was
introduced into a 100ml graduated cylinder. A weight of
35g was placed onto the center of the surface of the gel
and allowed to penetrate through the gel. The time taken
by the 35 g weight to penetrate 5 cm down through the gel
was noted for all formulations. The same procedures were
followed for each fresh formulation in triplicate and
average time was determined20.
In vitro release studies
The drug release studies were carried out in USP type II
dissolution test apparatus (DA6D, Bombay, India) at 37 ±
0.5°C and at 50 rpm. This speed was slow enough to avoid
the breaking of gelled formulation and maintained the
mild agitation conditions believed to exist in vivo.
Dissolution medium was 900 ml of 0.1N HCl buffer solution
(pH 1.2). A specified amount of in situ gel (5ml) equivalent
to 20 mg of LEF was used for test. 5 ml of aliquots were
withdrawn at predetermined time intervals. The
withdrawn samples were replaced immediately with an
equal volume of fresh buffer. The samples were filtered
and assayed spectrophotometrically at λmax 260 nm. The
measurements were carried out in triplicates and the
results were presented as percentage of cumulative LEF
released against each corresponding time21.
Kinetics analysis of drug release data
The dissolution profile of all the batches were fitted to
zero-order, first-order, second-o8rder and Higuchi kinetics
to ascertain the kinetic modeling of drug release by using
a PCP Disso Version 2.08 software, and the model with the
higher correlation coefficient was considered to be the
best fit model22.
Ex-vivo Gelation study
The best formula was subjected to ex-vivo gelation study
to check in situ gel formation in stomach. Six male albino
rats weighing 200–220 g was randomly divided into two
groups (three animals per group). Group -1: served as
Int. J. Pharm. Sci. Rev. Res., 64(2), September - October 2020; Article No. 02, Pages: 8-16 ISSN 0976 – 044X
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11
control and Group -2: served as treated. The animals were
fasted for 24 h prior to the experiment but allowed free
access to water. The amount of drug for tested group was
equivalent to 2 mg/kg. Control animals in group -1 were
administered normal saline orally and then, sacrificed and
stomach was removed, cut along with the greater
curvature. While rats in group-2 were administered
selected in situ gel formulation orally and after 3 h animals
were sacrificed. Stomach was removed outside and cut
along with the greater curvature to observe weather gel
forms or not23.
RESULTS AND DISCUSSION
Drug - polymer compatibility studies
Fourier Transform Infrared spectroscopy (FTIR)
The compatibility of LEF with the excipients was confirmed
by FTIR spectroscopy. The FTIR spectrum of LEF alone is
illustrated in figure (1-a) which characterized by clear
sharp characteristic peak at 3356 cm-1. This peak is
attributed to N-H stretching band of secondary amine
group and a sharp peak appearing at 3066 cm-1 in spectrum
which is assigned to C-H stretching vibration of benzene
ring. At low frequencies, a sharp peak appears at 1693 cm-
1 is attributed to HC=N-O group in isoxazole ring. Also, a
sharp peak at 1604 cm-1 is assigned to C=O of amide and a
peak at 1539 cm-1 is attributed to C=C9, 10.
An IR spectrum of sodium alginate alone is shown in figure
(1-b) exhibited major band at 3417 cm-1 at high frequency
for OH group. The band at 2935 cm-1 was due to –CH2
group. In addition, bands at 1415 and 1604 cm-1 which are
characteristic to asymmetric and symmetric stretching
bands of carboxylate salt group –COO. The band at 1033
cm-1 was due to C-O-C stretching vibration24. FTIR
spectrum of physical mixture of LEF and sodium alginate
(1:1w/w) is shown in figure (1-c). It was observed that
principle peaks of drug were found to be in FTIR spectrum
of physical mixture of drug and polymer at the same
positions. It was suggested that there was no physical or
chemical interaction between drug and polymer.
Figure 1: FTIR spectra of (a) LEF, (b) sodium alginate, (c) LEF- sodium alginate physical mixture (1:1 w/w)
Differential Scanning Calorimetry (DSC)
Interactions in the samples are derived from DSC by
changes in the thermal events, such as elimination of an
endotherm or exotherm peak, or appearance of a new
peak.
Figure (2-a) shows the DSC thermogram of LEF alone which
is characterized by sharp endothermic peak at 166.06°C
corresponds the melting point of drug indicating its
crystalline nature. This is in good agreement with the
previous finding on thermal analysis of LEF by Krishnan et
al., 2018 25.
Figure (2-b) shows the DSC thermogram of sodium alginate
alone which is characterized by endothermic peak at
119.16°C due to removal of absorbed moisture, finally a
sharp exothermic peak at 235.84°C due to alginate
decomposition26.
The DSC thermogram of physical mixture of LEF and
sodium alginate (1:1 w/w) is shown in figure (2-c). The
thermogram shows the characteristic endothermic peak of
the drug with little shift at 164.67 ºC indicating
compatibility between drug and polymer.
Characterization of LEF in situ gel formulations for
selection of working concentration range of gelling
polymer and complexing agent
Selection of working concentration range of gelling
polymer
All the prepared formulations had off-white appearance
and showed no lumps in the preparation as shown in figure
(3). The formulations did not produce any gelation at room
temperature.
Int. J. Pharm. Sci. Rev. Res., 64(2), September - October 2020; Article No. 02, Pages: 8-16 ISSN 0976 – 044X
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12
Figure 2: DSC thermograms of (a) LEF, (b) sodium alginate, (c) LEF-sodium alginate physical mixture (1:1 w/w)
Figure 3: In situ gel formulation of LE, (a) in situ gel solution at room temperature, (b) floating in situ gel at pH 1.2
As shown in table (1), Batches S1 to S5 were prepared to
study the effect of sodium alginate concentration on the
floating lag time and gel strength, pH, density and the
other physical properties of the gel in pH 1.2.
The pH values were determined for each in situ gel
formulations and the results were revealed in table (1). The
formulations possessed satisfactory pH value ranging from
8.62 to 9.2 which is suitable to maintain the formulations
in a liquid state. Aqueous solutions of sodium alginate are
most stable at pH range of 4–10. Below pH 3, alginic acid is
precipitated from the alginate solution making the
formulation unsightly containing gel and liquid phases5.
All formulations have density lower than gastric content,
which is ~1.004 g/cm3, thus ensuring their buoyancy. As
shown in table (1), the densities of formulations were
ranged between 0.350-0.73 g/cm3 11.
All the formulations showed good gel strength which
ranged from 17 -42 sec. Gel strength demonstrates the
ability of the gelled mass to withstand the peristaltic
movement in "in- vivo".
The solutions showed a marked increase in viscosity with
increasing concentration of sodium alginate (0. 5 – 2.5 %
w/v). This is attributed to a consequence of increasing
chain interaction with an increase in polymer
concentration19.
S1 and S2 formulations which contain low concentration of
sodium alginate showed improper gelation when
contacted with 0.1 N HCL (pH 1.2) which leads to a rapid
flow of the formulation and also the time required for
gelation was also very long. Formulations which contain
higher concentrations of sodium alginate showed
instantaneous gelation when contacted with 0.1 N HCl (pH
1.2) but the viscosity of the solutions is high so they were
difficult to be poured.
The gelling capacity for all formulations showed soft gel
formation which dispersed within 4hr, S2 batch showed
immediate gelation that remains for 8 h (++) while S3 to S5
batches showed immediate gelation that remains for more
than 12 hours (+++). It is obvious that, sodium alginate at
1% concentration form stiff gel while below 1%, gel is
formed but ruptured, and these results are in agreement
with chaniyara et al., 2013 27. Among all of these batches
(from S1 to S5), batch S3 has optimum viscosity (245.6 cp)
and has enough gel capacity.
From figure (4), it is obvious that increasing the polymer
concentration in the prepared formulations caused
decrease in rate of drug release. This effect is attributed to
increase of the polymer concentration, more polymeric
chains are available for crosslinking with the calcium ion.
As the crosslinking increases, it forms a stronger gel, across
which drug diffusion becomes difficult28. Table (2) shows
the kinetic analysis of the in-vitro dissolution data of LEF
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13
from different in situ gels. According to correlation
coefficient (r), it was found that the in-vitro release of LEF
from different in situ gels followed zero- order model.
On bases of these evaluation parameters, S3 was selected
as promising formula. So, working concentration of sodium
alginate that was selected is 1.5% w/v for further studies.
Selection of working concentration range of complexing
agent
The pH values were determined for each in situ gel
formulations and the results are shown in table (3). The
formulations possessed satisfactory pH value ranging from
9.01 to 9.3 which is suitable to maintain the formulations
in a liquid state.
All formulations have density lower than gastric content
which is ~1.004 g/cm3, thus ensuring their buoyancy11. As
shown in table (3), the densities of formulations were
found to be ranged between 0.417-0.730 g/cm3. All the
formulations showed good gel strength which ranged from
20 -46 sec.
As revealed in table (3), five batches (C1 to C5) were
prepared with increasing concentration of calcium
carbonate from 0.25 -1.5% w/v.
Batches C1 and C2, gel was formed but it ruptured and
exhibit fragmentation in 3-4 h due to poor crosslinking of
calcium ion because of low concentration of calcium
carbonate.
Increasing calcium carbonate content in the formulation
increased the viscosity of the formulations. Since the
calcium carbonate is present in the formulations as
insoluble dispersion, an increase in its concentration
proportionally increased the number of particles
dispersed, thus contributing to increased viscosity17.
C1and C2 formulations which contain low concentration of
calcium carbonate showed the lowest floating behavior. In
C5 batch, viscosity of the solutions was very high (446.5 cp)
because of the higher concentration of calcium carbonate
which leads to difficulty in pouring the solution.
From figure (5), it was observed that the drug release
decreased as concentration of calcium carbonate in
formulation increased. This may be attributed to the fact
that as the concentration of calcium ions increases, cross-
linking also increases. Only batches C4 and C5 containing
1% and 1.5% w/v of calcium carbonate, respectively, have
cumulative percent release for more than 6 h suggesting
better stiffness of gel.
Table 1: Composition and Evaluation of LEF in situ gels (S1-S5) for selection of working concentration ranges of gelling
polymer (sodium alginate)
Ba tches
Sod. Alginate (%)
pH
Floating
properties
Viscosity (cps)
In vitr o gel
ca pacity
De nsit y (g/c m3)
Dr ug C ontent (%)
Ge l st rength (sec)
po urabilit y
FLT (sec)
FD (h)
S1
0.5
8.62±0.4
180±10
<8
155.6±21
+
0.350±0.23
98.5±1.13
17±4
Easy
S2
1
8.65±0.2
95±14
<12
215.4±40
++
0.417±0.17
101.5±0.94
23±8
Easy
S3
1.5
8.66±0.5
66±9
>12
245.6±32
+++
0.510±0.27
102.3±0.53
31±5
Pourable
S4
2
8.91±0.3
60±12
>12
404.7±28
+++
0.670±0.14
99.5±1.32
37±4
Difficult
S5
2.5
9.21±0.1
47±15
>12
498.5±36
+++
0.730±0.06
97.5±1.67
42±6
Difficult
* FLT: Floating lag time, FD: floating duration, all formulations contain 400mg LEF, 0.5% CaCO3 and 0.25% w/v sodium
citrate.
Figure 4: Effect of sodium alginate concentration on in- vitro drug release profile
0
20
40
60
80
100
012345678
% Drug Released
Time in hours
S1
S2
S3
S4
S5
Int. J. Pharm. Sci. Rev. Res., 64(2), September - October 2020; Article No. 02, Pages: 8-16 ISSN 0976 – 044X
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14
Table 2: Kinetics parameters calculated for dissolution data of LEF from in situ gel formulations (S1-S5) according to Zero,
First, Second and Higuchi models
Table (4) shows the kinetic analysis of the in-vitro
dissolution data of LEF from different in situ gels.
According to correlation coefficient (r), it was found that
the in-vitro release of LEF from different in situ gels
followed zero- order model.
It is obvious that, among all of these batches (from C1 to
C5), batch C4 has optimum viscosity, enough gel capacity
and showed cumulative drug release for more than 6 hrs.
On basis of these evaluation parameters and release
profile, C4 was selected as promising formula. So, working
concentration of calcium carbonate that was selected is 1%
w/v for further ex-vivo studies.
Table 3: formulation and Evaluation of LEF in situ gels (C1-C5) for selection of working concentration ranges of complexing
agent (calcium carbonate)
Ba tches
Sod. Alginate (%)
pH
Floating properties
Viscosity (cps)
In vitr o ge l
ca pacity
De nsit y (g/c m3)
Dr ug C ontent
(% )
Ge l
st rength(s e c)
po urabilit y
FLT (sec)
FD (h)
C1
0.25
9.01±0.2
350±6
<6
135.7±31
+
0.417±0.18
99.1±1.7
20±6
Easy
C2
0.5
9.25±0.1
175±9
<12
178.4±16
+
0.457±0.29
101.3±1.2
32±7
Easy
C3
0.75
9.18±0.2
86±3
>12
205.5±36
++
0.525±0.14
98.6±2.4
35±9
Pourable
C4
1
9.2±0.4
40±2
>12
295.4±28
+++
0.570±0.21
99.5±1.6
45±12
Pourable
C5
1.5
9.3±0.08
47±5
>12
446.5±18
+++
0.732±0.09
102.5±0.4
46±15
Difficult
* FLT: Floating lag time, FD: floating duration, all formulations contain 400mg LEF, 1.5% sodium alginate and 0.25% w/v sodium citrate.
Batch
Parameter
Zero
First
Second
Higuchi
Best model
S1
A
57.733
2.584
-1.484
35.343
Zero
B
13.305
-0.899
1.144
35.454
R
0.970
-0.899
0.869
0.949
K
13.305
-2.071
1.144
35.454
t1/2
3.758
-0.335
0.009
1.989
S2
A
60.052
2.846
-39.954
41.216
Zero
B
7.902
-0.746
20.001
25.376
R
0.999
-0.801
0.708
0.987
K
7.902
-1.718
20.001
25.376
t1/2
6.328
-0.403
0.000
3.882
S3
A
18.956
2.999
-39.964
47.296
Zero
B
37.018
-0.794
20.007
11.240
R
0.991
-0.839
0.708
0.977
K
37.018
-1.828
20.007
11.240
t1/2
1.824
-0.379
0.000
4.448
S4
A
10.861
2.236
-0.382
41.549
Zero
B
37.321
-0.334
0.183
10.482
R
0.993
-0.950
0.733
0.990
K
37.321
-0.770
0.183
10.482
t1/2
1.795
-0.900
0.055
4.770
S5
A
24.613
2.310
-0.234
-3.959
Zero
B
11.014
-0.268
0.109
37.180
R
0.966
-0.795
0.674
0.937
K
11.014
-0.617
0.109
37.180
t1/2
4.540
-1.123
0.091
1.809
Int. J. Pharm. Sci. Rev. Res., 64(2), September - October 2020; Article No. 02, Pages: 8-16 ISSN 0976 – 044X
International Journal of Pharmaceutical Sciences Review and Research
International Journal of Pharmaceutical Sciences Review and Research
Available online at www.globalresearchonline.net
©Copyright protected. Unauthorised republication, reproduction, distribution, dissemina tion and copying of this document in whole or in part is strictly prohibited.
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15
Figure 5: Effect of calcium carbonate concentration on the in-vitro drug release profile
Table 4: Kinetics parameters calculated for dissolution data of LEF from in-situ gel formulations (C1-C5) according to Zero,
First, Second and Higuchi models
Formulae
Parameter
Zero
First
Second
Higuchi
Best model
C1
a
37.587
2.441
-0.312
2.872
Zero
B
19.970
-0.676
0.257
54.016
r
0.998
-0.939
0.881
0.991
k
19.970
-1.556
0.257
54.016
t1/2
2.504
-0.445
0.039
0.857
C2
a
38.267
2.202
-0.173
9.892
Zero
b
11.881
-0.325
0.102
38.186
r
0.995
-0.912
0.771
0.984
k
11.881
-0.749
0.102
38.186
t1/2
4.208
-0.926
0.098
1.714
C3
a
31.250
2.770
-3.972
3.097
Zero
b
12.350
-0.568
1.998
38.893
r
0.952
-0.774
0.708
0.923
k
12.350
-1.309
1.998
38.893
t1/2
4.049
-0.530
0.005
1.653
C4
a
30.383
2.174
-0.125
2.731
Zero
b
9.233
-0.204
0.056
33.544
r
0.994
-0.863
0.678
0.977
k
9.233
-0.469
0.056
33.544
t1/2
5.415
-1.477
0.178
2.222
C5
a
24.644
2.860
-28.552
-4.608
Zero
b
9.863
-0.445
10.715
35.683
r
0.982
-0.704
0.613
0.961
k
9.863
-1.026
10.715
35.683
t1/2
5.070
-0.675
0.001
1.963
Ex-vivo Gelation study
Results of ex-vivo gelation study showed that when the
group 2 animals are sacrificed after 3hr, the gel formed in
their stomach. It was observed that formed gel remained
on a mucosal layer of the stomach to release the drug in a
controlled manner (Figure 6).
Figure 6: Ex-vivo gelation study
0
20
40
60
80
100
012345678
% Drug Released
Time in hours
C1
C2
C3
C4
C5
Int. J. Pharm. Sci. Rev. Res., 64(2), September - October 2020; Article No. 02, Pages: 8-16 ISSN 0976 – 044X
International Journal of Pharmaceutical Sciences Review and Research
International Journal of Pharmaceutical Sciences Review and Research
Available online at www.globalresearchonline.net
©Copyright protected. Unauthorised republication, reproduction, distribution, dissemina tion and copying of this document in whole or in part is strictly prohibited.
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16
CONCLUSION
In the present study in situ gel of LEF was prepared by using
calcium carbonate and sodium alginate of different
concentration from (0.25- 1.5% w/v) and (0.5-2.5% w/v).
All the prepared formulation was evaluated in order to
determine the suitability for the formulation. Formula C4
(containing 1.5% w/v sodium alginate and 1% w/v calcium
carbonate and 0.25% sodium citrate) was considered the
best formula since it showed minimum floating lag time
(40 sec), optimum viscosity (295.4 cps), and gel strength
(45 sec) , optimum drug release (98%) for more than 6 h
and good gel formation ex-vivo. On basis of preliminary
studies, the best concentrations of sodium alginate and
calcium carbonate selected for floating in situ gel
formation are 1.5% and 1% respectively.
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Source of Support: None declared.
Conflict of Interest: None declared.
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