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Transl Clin Pharmacol
Vol. 23, No.1, June 30, 2015
http://dx.doi.org/10.12793/tcp.2015.23.1.26
2015;23(1):26-30
Bioequivalence study of Donepezil
hydrochloride in healthy Korean volunteers
Yewon Choi1, Su-jin Rhee1, In-Jin Jang1, Kyung-Sang Yu1, Sung-Vin Yim2 and Bo-Hyung Kim2*
1Department of Clinical Pharmacology and erapeutics, Seoul National University College of Medicine and Hospital, Seoul 110-744,
Korea, 2Department of Clinical Pharmacology and erapeutics, Kyung Hee University College of Medicine and Hospital, Seoul 130-
872, Korea
*Correspondence: B. H. Kim; Tel: +82-2-958-9326, Fax: +82-2-958-9559, E-mail: bhkim98@khu.ac.kr
Donepezil is a centrally acting, reversible acetylcholinesterase inhibitor that is widely used for treat-
ing Alzheimer’s disease. is study aimed to compare the pharmacokinetics of Bastia®, a test tablet
formulation of donepezil hydrochloride 10 mg, with those of Aricept®, the reference tablet formula-
tion of donepezil hydrochloride 10 mg, in healthy Korean male volunteers. A randomized, single-
dose, two-way crossover study was conducted in 32 subjects. Subjects received a single dose of ei-
ther test or reference compound and the alternate drug aer a 4-week washout period. Serial blood
samples for pharmacokinetic analysis were collected prior to dosing and periodically for 288 h aer
dosing for measurement of the plasma concentrations of donepezil. A non-compartmental method
was used to estimate the pharmacokinetic parameters. e maximum concentration (Cmax) and the
area under the concentration-time curve from time zero to the time of the last quantiable concen-
tration (AUC288h) for the two formulations were compared to evaluate bioequivalence. e Cmax of
the test and reference drugs were 27.58±7.46 and 26.35±6.51 μg/L (mean±SD), respectively, while
AUC288h was 1080.14±229.77 and 1043.07±242.28 μg·h/L (mean±SD), respectively. e geometric
mean ratios (90% condence interval) of the Cmax and AUC288h of the two tablets were 1.043 (0.990-
1.099) and 1.039 (1.013-1.065). In conclusion, the newly formulated tablet of donepezil hydrochlo-
ride 10 mg is bioequivalent to the currently marketed 10 mg tablet.
Introduction
Donepezil is a piperidine-based, reversible acetylcholinester-
ase inhibitor widely used for treating Alzheimer’s disease. Its
therapeutic effect is thought to result from increased levels of
acetylcholine available for synaptic transmission in the central
nervous system. When compared to placebo, daily doses of 5
or 10 mg donepezil improve both cognitive and global clinical
functions in patients with mild to moderate Alzheimer’s disease.
A daily dose of 10 mg delays the deterioration in the activities
of daily life compared to that observed with placebo treatment.
[1] e daily-recommended dose of donepezil is 5 to 10 mg.[2]
The dose can be increased depending on the patient’s clinical
condition.
In one study, the concentration of donepezil peaked (Cmax) to
4.1±1.5 h aer dosing and the mean terminal half-life was found
to be 81.5±22.0 h.[3] e pharmacokinetics (PK) of donepezil
were found to be linear and showed dose proportionality aer
the administration of single doses to healthy volunteers.[3] e
elimination half-life of donepezil is about 70 h and the mean ap-
parent plasma clearance (CL/F) is 0.13-0.19 L/h/kg. Donepezil
is slowly absorbed from the gastrointestinal tract. Its absorption
rate and extent of absorption are not influenced by food. Its
relative oral bioavailability is 100%. e drug is excreted in the
parent form by the kidney and extensively metabolized, mainly
by CYP 3A4 and CYP 2D6, in the liver. The metabolites are
mainly excreted into the feces through the bile.[4]
Bastia® is a generic preparation of donepezil hydrochloride,
developed by Korea Pharma Co., Ltd. Although the innovator
and the generic preparations are manufactured by different
manufacturers, generic formulations can provide alternative
therapeutic options if they are bioequivalent to the innovator
preparation.
e aim of this study was to compare the PK of Bastia® (test
Copyright © 2015 Translational and Clinical Pharmacology
It is identical to the Creative Commons Attribution Non-Commercial License
(http://creativecommons.org/licenses/by-nc/3.0/).
This paper meets the requirement of KS X ISO 9706, ISO 9706-1994 and
ANSI/NISO Z.39.48-1992 (Permanence of Paper).
ORIGINAL ARTICLE
Received 14 May 2015
Revised 4 Jun 2015
Accepted 5 Jun 2015
Keywords
Bioequivalence,
Pharmacokinetics,
Donepezil
pISSN: 2289-0882
eISSN: 2383-5427
Vol. 23, No.1, June 30, 2015
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Transl Clin Pharmacol
drug) and Aricept® (reference drug) in healthy Korean male
volunteers and to evaluate the bioequivalence of the two formu-
lations.
Methods
Subjects
irty-two healthy Korean male subjects aged 19- to 55-years-
old, with no history of gastrointestinal, cardiovascular, pulmo-
nary, renal, neurologic, endocrinal, or hematologic disease, and
with no hypersensitivity to medications were recruited in this
study. ey were not taking any other medications at the time
of screening. All subjects submitted written informed consents
before participating in the study. is study was approved by the
Institutional Review Board of Kyung Hee University Hospital.
Drugs
e test formulation (donepezil hydrochloride, tablet 10 mg)
was manufactured by Korea Pharma Co., Ltd., Seoul, Korea
(lot no. 9005, Expiration 2012. 11. 25). e reference formula-
tion (donepezil hydrochloride, tablet 10 mg) was manufactured
by Daewoong Pharmaceutical Co., Ltd., Seoul, Korea (lot no.
055506, Manufactured 2009. 7. 8).
Study design
A randomized, single-dose, two-period, two-treatment, two-
sequence, crossover study was conducted with 32 subjects ran-
domized into 2 sequence groups. e number of subjects was
calculated using published intra-individual coecient of varia-
tion of Cmax and AUCinf, (15% and 10%, respectively[5]), and
considering dropouts . Subjects in one sequence group received
the reference formulation in period 1 and the test formulation in
period 2 with an interval of 4 weeks between periods, while sub-
jects in the other group received the drugs in the opposite order.
Subjects were admitted to the Clinical Trial Center, Kyung Hee
University Hospital, from the day before dosing (Day -1) to the
day aer dosing (Day 2) of each period. ey were instructed to
abstain from drinking alcohol, smoking, intense physical activ-
ity, and intake of drinks containing xanthine. Subjects received
one tablet of either the test or reference formulations with 240
mL of water in fasting state on the morning of the rst day of
each period. Water and food intake were restrained for 2 and 4
h, respectively, aer drug administration. Serial blood samples
for PK analysis were collected pre-dose (time 0), and at 1, 1.5,
2, 2.5, 3, 4, 6, 8, 12, 24, 48, 96, 144, 240, and 288 h aer dosing.
Safety and tolerability were assessed based on adverse events,
vital signs, 12-lead ECG, clinical laboratory values, and physical
examination.
Plasma concentration
Blood samples (7 mL each) were collected and plasma was sep-
arated by centrifugation at 3,000 rpm for 10 min at 4°C and im-
mediately stored at a temperature of -70°C or lower until analy-
sis. e plasma concentration of donepezil was determined by
high-performance liquid chromatography (HPLC, Agilent 1200
series, Agilent Technologies, USA) tandem mass spectrometry
(MS/MS, API 4000, Applied Biosystems/MDS SCIEX, Foster
City, CA, USA). Donepezil (100 μg/mL in 50% methanol) was
used as a reference standard.
Each plasma sample (300 μL) was mixed with 1,000 μL of cis-
apride (15 μg/mL in acetonitrile, internal standard), vortexed
for 90 sec, and centrifuged at 13,000 rpm for 8 min. e super-
natant (1,000 μL) was taken and evaporated under nitrogen
gas. e mobile phase (200 μL) was added and injected into the
HPLC system.
The calibration curve was obtained by fitting the peak area
ratio of the internal standard and the nominal concentration
(X) of analyte to the equation, Y=aX + b (weighting 1/X2). e
method was validated over the range of 0.1-50 ng/mL for done-
pezil, 5 times daily, for 5 days. e lower limit of quantitation
(LLOQ) was 0.1 ng/mL. Assay precisions were 96.92-113.58%
(interday) and 97.63-111.51% (intraday) and the coecients of
variation (CVs) were less than 2.96 % (0.25 ng/mL, interday)
and 5.40 % (5 ng/mL, intraday).
Pharmacokinetic analysis
e Cmax and the time to Cmax (tmax) were directly obtained from
the observed values. e area under the plasma concentration-
time curve from time 0 to the last observed time point of 288 h
(AUC288h) was calculated using the linear trapezoidal approxi-
mation. The terminal elimination rate constant (ke) was esti-
mated from the terminal phase by log-linear regression and the
terminal half-life was calculated as ln 2/ke. e AUC from time
0 to time innity (AUCinf) was calculated by adding AUC288h to
the extrapolated area beyond the last measurable plasma con-
centration (Clast), AUC288h + Clast/ke. e apparent clearance (CL/
F) was calculated as Dose/AUCinf. Pharmacokinetic parameters
were calculated and estimated as non-compartmental using the
BA Calc 2007 analysis program Ver. 1.0.0 (Ministry of Food and
Drug Safety, MFDS, Cheongju-si, Chungcheongbuk-do, Korea).
Statistical analysis
A general linear mixed eect model was used to compare the
Cmax and AUC288h between the test and reference formulations.
e period, sequence, and formulation variables were used as
fixed effects, and subjects nested within sequence were used
as random effects. In the mixed effect model, the logarithmic
forms of Cmax and AUC were used, and the least square mean
dierences of Cmax and AUC with 90% condence interval (90%
CI) between both formulations were exponentiated to obtain
the geometric mean ratio and its 90% CI. Bioequivalence was
assessed based on the criteria of conventional bioequivalence
with a range of 0.8-1.25. These statistical analyses were per-
formed using the K-BE Test 2007, Ver. 1.1.0 (Ministry of Food
and Drug Safety, MFDS, Cheongju-si, Chungcheongbuk-do,
Korea).
Yewon Choi, et al.
Vol. 23, No.1, June 30, 2015
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Transl Clin Pharmacol
RESULTS
e mean values of age, weight, and height of the 32 subjects
were 24.5±3.8 (19-39) years, 68.9±9.2 (56-90) kg, and 175.4±4.7
(165-184.4) cm, respectively (mean±SD (range)). Among the 32
subjects, 5 subjects were excluded because of non-compliance
and 2 subjects experienced adverse events (AEs). Vomiting was
reported 4 h aer administration of the reference tablet in one
subject and headache occurred 4 h aer administration of the
test tablet in another subject. ese two subjects were dropped
from the study. e remaining 25 subjects completed the study,
and donepezil was well-tolerated in these subjects .
The pharmacokinetic parameters for the reference and test
compounds are shown in Table 1. The concentration-time
curves for both formulations were similar, including both the
absorption and disposition phases (Fig. 1). e median tmax of
the test drug (2.0 h, range 1.5-3.0 h) was similar to that of the
reference drug (2.0 h, range 1.0-4.0 h), and the mean half-life
of donepezil was similar for the test (70.40±10.08 h) and refer-
ence (72.81±11.78 h) formulations. The ratios of the geomet-
ric means (90% CI) for Cmax, AUC288h, and AUCinf were 1.043
(0.990-1.099), 1.039 (1.013-1.065), and 1.035 (1.009-1.061),
respectively. e 90% CIs are within the bioequivalence range
of 0.800-1.250. e mean value of CL/F of the test formulation
was similar to that of the reference formulation (Table 1). In
addition, no systematic within-subject dierence was observed
for the Cmax and AUC288h of the reference and test formulations
Figure 1. Mean plasma concentration-time profiles of donepezil after single oral administration of reference formulation (filled circles) and test for-
mulation (open circles). Bars represent standard deviations. (Left, linear; right, log-linear)
Parameters
Reference
(N=25)
Test
(N=25)
Mean±SD CV(%) Mean±SD CV(%) Geometric mean ratio
(90% CI)b
tmax (h)a 2.0 (1.0-4.0) 2.0 (1.5-3.0)
Cmax (μg/L) 26.35±6.51 24.71 27.58±7.46 27.04 1.043 (0.990–1.099)
AUC144h (μg·h/L) 867.37±188.69 21.75 897.97±180.10 20.06 1.035 (1.010–1.062)
AUC240h (μg·h/L) 1008.30±230.20 22.83 1044.24±218.32 20.91 1.039 (1.013–1.064)
AUC288h (μg·h/L) 1043.07±242.28 23.23 1080.14±229.77 21.27 1.039 (1.013–1.065)
AUCinf (μg·h/L) 1108.44±268.52 24.23 1143.71±254.17 22.22 1.035 (1.009–1.061)
AUCextra144h
a (%) 20.37 (13.97-29.33) 21.98 (13.46-30.86)
AUCextra240h
a (%) 8.38 (4.80-15.25) 8.59 (4.51-13.53)
AUCextra288h
a (%) 5.26 (2.73-10.88) 5.30 (2.55-8.59)
Half-life (h) 72.81±11.78 16.18 70.4±10.08 14.31
CL/F (L/h) 9.65±2.87 29.77 9.27±2.63 28.42
Table 1. Pharmacokinetic parameters of donepezil administered as the reference drug and test formulation
All values, except for AUCextra144h, AUCextra240h and AUCextra288h, are presented as the arithmetic mean±standard deviation and coefficient of varia-
tion (%). tmax, time to peak concentration; Cmax, peak plasma concentration; AUCt, area under the plasma concentration-time curve from 0 to t h;
AUCextrat(%), % extrapolated AUCt which was calculated as [(AUCinf-AUCt) / AUCinf]; CL/F, apparent clearance. aMedian value [min – max]. bGeomet-
ric mean ratio of test/reference, exponentiation of least square mean difference (90% CI) of logarithmic transformed Cmax and AUC values.
Bioequivalence study of Donepezil hydrochloride
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Transl Clin Pharmacol
(Fig. 2).
Discussion
is study shows that the test formulation of donepezil, Bas-
tia®, as 10 mg tablets is bioequivalent to the reference formu-
lation, Aricept® (10 mg tablets), based on the 90% CI of the
geometric mean ratios of Cmax and AUC288h. The mean values
of AUCinf, half-life, and CL/F were similar for both formula-
tions. e observed pharmacokinetic values are consistent with
previously reported donepezil PK data.[3] Orally administered
donepezil (10 mg) was well tolerated. Of 32 participants who
received the drug, AEs were reported in only two subjects, one
aer receiving the test compound and the other aer receiving
the reference compound . These AEs have been reported in a
previous study[6] and occurred 4 h aer administration of the
reference or test tablets. erefore, these AEs were considered
to be drug-related.
is study was conducted according to a randomized two-way
crossover design, which is generally used for studying bioequiv-
alence. e blood-sampling period of 288 h was long enough to
completely characterize the absorption and elimination phases
of donepezil. Considering that the terminal half-life is 50-70 h,
as shown here and in the previous study, the washout period
of 4 weeks used in the present study is 10-fold higher than the
half-life of donepezil and is sucient to eliminate the rst dose
of the drug completely prior to the second administration.[3]
Furthermore, for 13 subjects, the donepezil concentrations
measured just prior to the second dose were below the LLOQ
and for the other subjects, the values ranged from 0.11 to 0.24
ng/mL, which are less than 1% of the Cmax concentration. us, a
washout period of 4 weeks is sucient to ensure that the drug is
eliminated and there is no carry-over eect in the second phase
of the study.
e sowares used to analyze the data, BA-Calc 2007 (Ver.1.0.0)
and K-BE Test 2007 (Ver 1.1.0), were originally developed in
2007 in the College of Pharmacy at Kyung-hee University in
Korea, with the support of the Ministry of Food and Drug
Safety.[7] However, there are other widely used soware pack-
ages for analyzing pharmacokinetic parameters and assessing
bioequivalence. ese include Phoenix® WinNonlin® (Ver. 6.3,
Pharsight, Mountain View, CA), which uses the same statistical
methodology to assess bioequivalence as that used in K-BE Test
2007. When the pharmacokinetic data from the current study
were analyzed using Phoenix® WinNonlin®, the results were
similar to those obtained by K-BE Test 2007. ere were minor
dierences in some parameter values, but the dierences were
less than 0.01% and did not affect the bioequivalence conclu-
sions.
Because the mean half-life of donepezil is long (50-70 h), the
sampling period had to be correspondingly long. This long
sampling schedule could aect subject compliance in terms of
admission periods and outpatient visits for pharmacokinetic
sampling. To account for this, data at longer sampling times,
240 and 288 h, could be omitted and a truncated AUC can be
used to evaluate bioequivalence. We additionally conducted
a bioequivalence analysis using a truncated AUC for the data
where AUCextra (%) was around 20% or less (Table 1). e 90%
CIs of the truncated AUCs (AUC144h and AUC240h) were similar
to AUC288h and AUCinf and were within the range of 0.8-1.25.
Therefore, the truncated AUCs, AUC144h or AUC240h, could be
used as surrogates for AUC288h to reduce sampling time for this
bioequivalence study.
Alzheimer’s disease occurs in the elderly. Previous pharma-
cokinetic studies have shown that the elimination half-life of
donepezil in elderly patients is almost twice as long as that in
young healthy volunteers.[8,9] However, the exposure of the
drug including Cmax, CL/F and AUC measured during therapeu-
tic drug monitoring of elderly patients with Alzheimer's disease
are comparable to those observed in young healthy volunteers.
The difference of the half-life between the two age groups is
probably due to a large distribution volume in the elderly. Still,
further clinical studies are required to assess age-related dier-
ences in the disposition of the drug.
e pharmacokinetics of donepezil obtained aer administra-
Figure 2. Individual subject’s Cmax and AUC288h values for donepezil reference formulation and test formulation (Left: AUC288h, Right: Cmax)
Yewon Choi, et al.
Vol. 23, No.1, June 30, 2015
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Transl Clin Pharmacol
tion of test and reference drugs show that both formulations
have similar pharmacokinetic characteristics and are bioequiva-
lent with respect to the 90% CIs of the geometric mean ratios
of Cmax and AUC. Both formulations were well tolerated. All of
these ndings suggest that Bastia® could be a therapeutic alter-
native for Aricept®.
Acknowledgements
is study was sponsored by Korea Pharma Co., Ltd., Korea.
Conflict of interest
e authors have no conicts of interest to disclose.
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Bioequivalence study of Donepezil hydrochloride
