Download COMPARATIVE BIOAVAILABILITY OF TWO LISINOPRIL

Int. J. Chem. Sci.: 8(4), 2010, 2808-2814
COMPARATIVE BIOAVAILABILITY OF TWO LISINOPRIL
FORMULATIONS AFTER SINGLE DOSE ADMINISTRATION
TO HEALTHY VOLUNTEERS
NAGHAM A. JASIMa, ADLA A. SALOMI* and FADHIL M. ABIDa
a
College of Medicine, Babylon University, IRAQ
Ministry of Science, and Technology, Baghdad, IRAQ
ABSTRACT
Two formulations of lisinopril (5 mg) were evaluated for bioequivalence after single dosing to 20
healthy volunteers. The study was conducted according to an open, randomized, 2-period crossover design
with a 1-week washout interval between doses. The concentrations of lisinopril were determined in plasma
at different times by HPLC method. The pharmacokinetic parameters AUC (0-36 hr)), Cmax, Tmax and t ½
were calculated and tested for bioequivalence after logarithmic transformation of data and ratios of tmax
were evaluated non-parametrically. The analysis of pharmacokinetic data revealed the following
test/reference ratios and their confident interval (90% CI): 0.887 (0.84-1.22) for AUC (0-36 hr), 0.95
(0.83-1.25) for Cmax and 1.0 (0.99-1.08) for the 90% CI for tmax was 0.94-1.07. All parameters showed
bioequivalence between both formulations (Samapril and Zestril). A discrete fall in both; systolic blood
pressure (SBP) and diastolic (DBP) blood pressure was observed after drug administration. The time
course of both the parameters was similar for the 2 formulations.
Key words: Bioavailability, Lisinopril, Angiotensin, HPLC.
INTRODUCTION
Lisinopril is an oral long-acting angiotensin converting enzyme inhibitor1,2. It is a
synthetic peptide derivative and is chemically described as (S)-1-[N2-(1-carboxy-3phenylpropyl)-L-lysyl]-L-proline dihydrate. Its empirical formula is C21H31N3O5.2H2O. It is
a white to off-white, crystalline powder, with a molecular weight of 441.53. It is soluble in
water and sparingly soluble in methanol and practically insoluble in ethanol.
It inhibits angiotensin-converting enzyme (ACE) in human subjects and animals.
ACE is a peptidyl dipeptidase that catalyzes the conversion of angiotensin I to the
vasoconstrictor substance, angiotensin II. Angiotensin II also stimulates aldosterone
________________________________________
*
Author for correspondence;
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secretion by the adrenal cortex. The beneficial effects of lisinopril in hypertension and heart
failure appear to result primarily from suppression of the renin-angiotensin-aldosterone
system. Inhibition of ACE results in decreased plasma angiotensin II, which leads to
decreased vasopressor activity and to decrease aldosterone secretion. The latter decrease
may result in a small increase of serum potassium. In hypertensive patients with normal
renal function treated with lisinopril alone for up to 24 weeks, the mean increase in serum
potassium was approximately 0.1 meq/L; however, approximately 15% of patients had
increases greater than 0.5 meq/L and approximately 6% had a decrease greater than 0.5
meq/L. Removal of angiotensin II. Negative feedback on rennin secretion leads to increased
plasma renin activity. The mechanism through, which lisinopril lowers blood pressure, is
believed to be primarily suppression of the renin-angiotensin-aldosterone system, so
lisinopril is antihypertensive even in patients with low-renin hypertension1,2. When lisinopril
is used in pregnancy during the second and third trimesters, AEC inhibitors can cause injury
and even death to the developing fetus. When pregnancy is detected, lisinopril should be
discontinued as soon as possible3.
EXPERIMENTAL
Materials and methods
Samapril 5 mg tablet as test drug was obtained from SDI, Sammera, and Zestril 5 mg
tablet was obtained from commercial market.
Study program
Twenty healthy, nonsmoking, male volunteers (mean age ± SD, 28.5 ± 4.94 years;
weight, 66.9 ± 8.59 kg; height, 168.5 ± 4.11 cm) in two groups took part in this study. All
volunteers gave written informed consent after they had received detailed instructions about
the study performance of the drug. All volunteers were in good physical health according to
physical examination, hematological and urinary laboratory tests. Subjects did not take any
other medications for at least 1 week prior to and throughout the study. Each subject fasted
overnight before the experiment. Tablets were swallowed with 150 mL water.
A light, normal lunch consisting of cheese, bread, tea, and water was given to all
subjects 4 hours after dosing. A washout period of 1 week was included between the
administrations of each product. In the second phase, the test and reference tablets were
crossed between the two groups of volunteers.
Blood sampling
The blood samples had been drawn from each volunteer after oral dose administration
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of 5 mg of test and reference drug, according to the randomization schedule, with 150 mL
drinking water. Blood samples (2 mL) were taken via an indwelling venous cannula at the
following times: before drug administration (0 hr), and 1, 2, 4, 7, 9, 12, 15, 18, 24 and 36 hr
after drug administration. Within 10 minutes of collection, blood samples were centrifuged at
3000 rpm for 10 min and after clot retraction from each sample, two aliquots of plasma were
transferred to labeled tubes. All samples were handled at room temperature before storage at
–20ºC until assays were performed.
High-performance liquid chromatographic (HPLC) analysis
Analysis was performed on Shimadzu liquid chromatograph model LC-10AVP, using
a normal phase high-performance liquid chromatographic (HPLC) method described
previously4. To 1 mL plasma in a 5-mL glass tube, 20 μL NaOH 1M and 20 μL 2-bromo 2acetonaphtone 0.02% solution in acetone were added. The mixture was left for 30 min. After
adding 20 μL phosphoric acid 20% and 1 mL acetonitrile and also mixing for 5 min, the
samples were centrifuged for 10 min and 500 μL aliquots were evaporated to dryness under
nitrogen. The residue was reconstituted in 150 μL acetonitrile and 100 μL was injected onto
the HPLC column (Supelcosil-NH2, 5 μm, 250 mm × 4.6 mm ID; USA). The mobile phase
was acetonitrile: 0.25 mM potassium phosphate (33 : 67 v/v). Detection was carried out at
Shimadzu 10Av detector set at 245 nm. The analytical method was fully validated in terms of
intra- and inter-day variations, accuracy, and percent recovery according to USP guidelines3.
The method was linear over a range of 25-800 ng/mL of drug in plasmas. The
coefficients of variation between-day was determined from quality control samples processed
together with each batch of samples. There were between 4.5% and 7.6% for concentrations
ranging between 20 ng/mL and 500 ng/mL and the accuracy was between 96– 102%. The
limit of quantification was found to be 20 ng/mL on the basis of signal-to-noise ratio.
Pharmacokinetics and metabolism
Following oral administration of lisinopril, peak serum concentrations of lisinopril
occur within about 7 hours, although there was a trend to a small delay in time taken to reach
peak serum concentrations in acute myocardial infarction patients. Declining serum
concentrations exhibit a prolonged terminal phase, which does not contribute to drug
accumulation. This terminal phase probably represents saturable binding to ACE and is not
proportional to dose4-7.
Lisinopril does not appear to be bound to other serum proteins. Lisinopril does not
undergo metabolism and is excreted unchanged entirely in the urine. The mean extent of
absorption of lisinopril is approximately 25%, with large intersubject variability (6-60%) at
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all doses tested (5-80 mg). Lisinopril absorption is not influenced by the presence of food in
the gastrointestinal tract. The absolute bioavailability of lisinopril is reduced to 16% in
patients with stable NYHA Class II-IV congestive heart failure8,9, and the volume of
distributions appears to be slightly smaller than that in normal subjects. The oral
bioavailability of lisinopril in patients with acute myocardial infarction is similar to that in
healthy volunteers10.
Impaired renal function decreases elimination of lisinopril, which is excreted
principally through the kidneys, but this decrease becomes clinically important only, when
the glomerular filtration rate is below 30 mL/min. Above this glomerular filtration rate, the
elimination half-life is little changed. With greater impairment; however, peak and trough
lisinopril levels increase, time to peak concentration increases and time to attain steady state
is prolonged. Older patients, on average, have (approximately doubled) higher blood levels
and area under the plasma concentration time (AUC) than younger patients. Lisinopril can
be removed by hemodialysis11,12.
To compare the rate and extent of absorption of lisinopril in both formulations, the
following pharmacokinetic variables were calculated for each volunteer and product, using
actual blood sampling times. The areas under the plasma concentration-time curves (AUC 036 hr) were calculated using the linear trapezoidal rule. The maximum plasma concentration
(Cmax) and time to reach maximum plasma concentration (Tmax) were obtained directly from
the plasma-concentration data.
The elimination rate constant was calculated by least-squares regression using the
last points of each curve. The pharmacokinetics parameter for test and reference drugs are
summarized in Table 1.
Table 1: Pharmacokinetic data of Samapril and Zestril 5 mg tablet; (n = 20)
Zestril (reference)
Samapril (test)
Variables
Unit
Mean
RSD %
Mean
RSD %
Cmax
ng/mL
170.33
4.029
162.1
7.15
Tmax
hr
7
AUC0-36
ng.hr/mL
3372.8
83.74
2994.1
369.67
Ke
hr-1
17.902
2.198
17.407
2.836
* RSD relative standard deviation
7
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Statistical analysis
The test and reference treatments in each study were compared with respect to
relevant pharmacokinetic variables using analysis of variance with volunteer, product and
period effects after a logarithmic transformation of the data. Point estimates and 90%
confidence intervals (CI) for the test/reference mean ratios of these variables were calculated.
Bioequivalence of the test and reference drugs was assessed on the basis of these CI, in
relation to the conventional bioequivalence range of 80 – 125%.
RESULTS AND DISCUSSION
The concentration of lisinopril in blood serum of the volunteers with various time
from 0-36 hr were measured by HPLC and the data were presented in Table 2, while the
pharmacokinetics parameters are tabulated in Table 3. The summaries of both
pharmacokinetic variables for test and reference drugs are given in Table 1. The mean
plasma lisinopril concentrations-time profile for both formulations and comparison between
them are constructed as shown in Fig. 1.
180
Zestril
Samapril
160
Concentration (ng/L)
140
120
100
80
60
40
20
0
0
5
10
15
20
25
Time (hr)
30
35
40
Fig. 1: Comparison of mean concentration-time profile of test drug Samapril and
reference drug Zestril
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The 90% CIs for the test/reference mean ratios of the plasma lisinopril
pharmacokinetic variables Cmax, AUC0-t and Tmax (as measures of the rate and extent of
absorption of lisinopril, respectively), all fell within the conventional bioequivalence range
of 80 – 125%. The test products (Samapril) are therefore bioequivalent to the reference
product (Zestril) with respect to the rate and the extent of absorption.
In conclusion, the results of this study showed that Samapril tablets manufactured in
SDI are comparable to Zestril brands and can produce acceptable plasma concentrations.
Table 2: Concentration of lisinopril in serum (ng/mL) with time after oral
administration of 5 mg lisnoapril for 20 healthy volunteers
(i) Samapril 5 mg tablet hr
No. of
subject
0
1
2
4
7
9
12
15
18
24
36
Mean
0 20.52 46.285 92.591 162.1
132.4
114.4
99.3
83.89 59.865 37.84
± SD
0 2.388
9.435
9.525
9.40
9.653 10.921 11.19
3.591
6.448
7.159
(ii) Zestril 5 mg tablet
Mean
0
25.5
47.39
± SD
0
4.469 4.931
97.9 170.33 148.9
131.4 118.9
101.4
80.4
64.4
4.806
3.304 3.423
2.941
4.954
8.44
4.029
2.711
Table 3: Pharmacokinetics parameter of both lisinopril 5 mg tablet
(i) Samapril 5 mg tablet
Subject
No.
Ka
Ka 0.5t
Kelem.
Kelem 0.5t
Cmax
Tmax
AUC
Mean
0.487
1.428
0.041
17.407
7
162.1
2944.14
± SD
0.031
0.090
0.006
2.836
0
7.159
369.678
(ii) Zestril 5 mg tablet
Mean
0.458
1.529
0.039
17.902
7
170.33
3372.8
± SD
0.046
0.155
0.004
2.198
0
4.029
83.740
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Accepted : 30.11.2010