On the determination of bioequivalence

Pharmacokinetic comparison of orally disintegrating and conventional donepezil formulations in healthy Korean male subjects: a single-dose, randomized, open-label, 2-sequence, 2-period crossover study

BACKGROUND

Donepezil is a potent inhibitor of acetylcholinesterase, an enzyme that is targeted in the treatment of Alzheimer's disease.

OBJECTIVE

The purpose of this study was to compare the pharmacokinetic characteristics of orally disintegrating (test) and conventional (reference) donepezil formulations to satisfy the regulatory requirement for marketing.

METHODS

A single-center randomized, single-dose, open-label, 2-way crossover study with a 21-day washout period was conducted in 22 healthy volunteers. Plasma samples for the analysis of donepezil were collected up to 240 hours after drug administration. Participants received either reference or test drug formulation of 10 mg donepezil in the first period and the alternative formulation in the second period. Plasma concentrations of donepezil were determined by validated high-performance liquid chromatography coupled to tandem mass spectrometry detection. Pharmacokinetic parameters, including C(max) and AUC, were determined by noncompartmental analysis. ANOVA was carried out using log-transformed C(max) and AUC, and the mean ratios and their 90% CIs were calculated. The safety profiles and tolerabilities of the 2 formulations were also assessed based on laboratory tests, 12-lead ECGs, vital signs, and physical examinations.

RESULTS

Of the 22 participants initially enrolled, 18 healthy Korean participants completed both treatment periods. Four subjects did not complete both treatments: 3 subjects withdrew consent for personal reasons, and 1 subject experienced adverse events. No significant differences in pharmacokinetic parameters between the 2 formulations were observed. The mean (SD) age, height, and weight of the participants were 25.8 (4.1) years, 173.6 (5.7) cm, and 68.9 (7.8) kg, respectively. The mean (SD) C(max), AUC(last), and AUC(inf) for the reference formulation were 33.26 (6.58) ng/mL, 1521.69 (344.04) ng × h/mL, and 1691.46 (443.05) ng × h/mL, respectively. Corresponding values for the test formulation were 34.23 (6.79) ng/mL, 1554.33 (390.23) ng × h/mL, and 1718.27 (447.03) ng × h/mL, respectively. The median T(max) was 2 hours (range, 1-3 hours) for the reference and test formulations. The geometric mean ratios (90% CI) between the 2 formulations of donepezil were 102.9 (96.8-109.5) for C(max), 102.3 (96.1-108.9) for AUC(last), and 101.6 (95.4-108.2) for AUC(0-∞), respectively. During the study, 15 and 14 adverse events were reported for the reference and test formulations, respectively, and all were transient, mild, and resolved during the treatment period. These adverse events included 7 cases of nausea, 3 cases of headache, and 1 case each of dizziness, vomiting, chills, and sweating. All adverse events were considered related to the study drugs.

CONCLUSION

This study found that the test and reference formulations met the regulatory criteria for pharmacokinetic equivalence in these fasting healthy Korean male subjects. Both donepezil formulations appeared to be generally well tolerated.

When is a metric not a metric? Remarks on direct curve comparison in bioequivalence studies

The majority of measures proposed to date for direct curve comparison in bioequivalence studies were investigated. These measures have often been called metrics, but in most cases this was incorrect in the mathematical sense. It was demonstrated, with a set of counter-examples, that the axioms of a metric are fulfilled only for the integral p-metric and some of its transforms. The Rescigno index and two other measures devised by Polli and McLean are the semi-metrics, lacking the triangle inequality, while others also lack symmetry. The use of the p-metric is therefore recommended, and statistical analysis is suggested as a point at which the scaling of differences might be carried out.

Bioequivalence Evaluation of Two Formulations of Doxazosin Tablet in Healthy Thai Male Volunteers

The bioequivalence of two doxazosin 2 mg tablets was determined in 24 healthy Thai male volunteers after one single dose in a randomized cross-over study with a one week washout period. The study was conducted at Faculty of Pharmaceutical Sciences and Health Sciences Research Institute, Naresuan University, Phitsanulok, Thailand. Reference (Cardura, Heinrich Mack Nachf. GmbH & Co. GK, Illertissen, Germany) and test (Dozozin-2, Umeda Co., Ltd., Bangkok Thailand) were administered to volunteers after overnight fasting. Blood samples were collected at specified time intervals and plasma was separated. The validated HPLC method with fluorescence detection was used for quantification of doxazosin in plasma samples. The pharmacokinetic parameters, T(max), C(max), AUC(t), AUC(infinity), T(1/2), lambda(z), Cl and V(d), were determined from plasma concentration time profile of both formulations by using non-compartment analysis. The calculated pharmacokinetic parameters were compared statistically to evaluate bioequivalence between the two brands. The analysis of variance (ANOVA) using log-transformed C(max), AUC(t), and AUC(infinity) did not show any significant difference between two formulations. The point estimates and 90% confidence intervals for C(max), AUC(t) and AUC(infinity) were within the acceptance range (0.80-1.25), satisfying the bioequivalence criteria of the Thailand Food and Drug Administration Guidelines. These results indicate that Dozozin-2 is bioequivalent to Cardura and, thus, may be prescribed interchangeably.

Evaluation of Bioequivalence of Two Formulations Containing 100 Milligrams of Aceclofenac

The bioequivalence of two oral formulations containing aceclofenac 100 mg was determined in 24 healthy Indian male volunteers. The study was designed as a single dose, fasting, two-period two-sequence crossover study with a washout period of 1 week. The content of aceclofenac in plasma was determined by a validated HPLC method with UV detection. The preparations were compared using the parameters area under the plasma concentration-time curve (AUC0-t), area under the plasma concentration-time curve from zero to infinity (AUC0-infinity), peak plasma concentration (Cmax), and time to reach peak plasma concentration (tmax). No statistically significant difference was observed between the logarithmic transformed AUC0-infinity and Cmax values of the two preparations. The 90% confidence interval for the ratio of the logarithmic transformed AUC0-t, AUC0-infinity, and Cmax were within the bioequivalence limit of 0.80-1.25.

Pharmacokinetic and pharmacodynamic characteristics of a new S-amlodipine formulation in healthy Korean male subjects: A randomized, open-label, two-period, comparative, crossover study

BACKGROUND

Amlodipine, a dihydropyridine calcium channel antagonist, is prescribed for the management of angina and hypertension. It is used therapeutically as a racemic mixture, composed of S- and R-enantiomers, but its calcium channel-blocking effect is confined to S-amlodipine; R-amlodipine has 1000-fold less activity than its S-enantiomer.

OBJECTIVE

The objective of this study was to compare the pharmacokinetic and pharmacodynamic properties and safety profiles of a newly developed amlodipine formulation, composed wholly of S-amlodipine, with those of the conventionally prescribed racemic formulation.

METHODS

This randomized, open-label, 2-period, comparative, crossover study was conducted with healthy volunteers at the Gil Medical Center and Gachon Medical School, Incheon, Korea. Male subjects, aged 20 to 50 years, were eligible to participate if their weight was within 20% of ideal body weight and if they were judged by physicians to be healthy. All subjects were randomly assigned in a 1:1 ratio to 1 of 2 treatment sequences: (1) a single dose of the test amlodipine formulation (S-enantiomer amlodipine 5 mg p.o.) (Lodien [Hanlim Pharmaceutical Co., Seoul, Korea]) in the first study period, followed by a single dose of the reference amlodipine formulation (racemate 10 mg p.o.) (Norvasc [Pfizer Pharmaceuticals Korea Ltd., Seoul, Korea]) in the second study period, or (2) a single dose of the reference formulation in the first study period, followed by a single dose of the test formulation in the second period. A 3-week washout occurred between study periods. Blood samples for pharmacokinetic analysis of S-amlodipine were collected at 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 24, 48, 72, 96, 120, 144, and 168 hours after drug administration. Pharmacodynamic variables (ie, systolic and diastolic blood pressure and heart rate) were measured at 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 24, 48, and 72 hours after administration. Safety profiles were also assessed. Hematology, biochemistry, electrocardiography, and urinalysis were performed at baseline and end of study. Adverse events were monitored throughout the study period. Pharmacokinetic characteristics were compared using noncompartmental analysis. Pharmacokinetic equivalence was concluded if the geometric mean ratios of the plasma Cmax and AUC were within the predetermined range of 80% to 125%.

RESULTS

Twenty-six healthy Korean male volunteers were screened and 18 subjects (mean [SD] age, 23.4 [1.5] years [range, 21-26 years]; mean [SD] weight, 69.3 [6.8] kg [range, 60-88 kg]) were enrolled and completed the study. The plasma concentration-time profiles of S-amlodipine were comparable after administration of both formulations. The mean (SD) values for Cmax AUC from time 0 to the last available measurement (AUC(last)), and AUC from 0 to infinity (AUC(0-infinity)) for the reference formulation (3.0 [0.6] ng/mL, 151.4 [35.7] ng x h/mL, and 175.3 [45.1] ng x h/mL, respectively) did not differ significantly from those for the test formulation (3.1 [0.6] ng/mL, 139.7 [40.3] ng x h/mL, and 161.7 [43.8] ng x h/mL, respectively). The calculated 90% Cls for the corresponding ratios of log-transformed Cmax, AUCO(0-infinity), and AUC(last) were 97.56% to 112.51%, 86.31% to 98.74%, and 83.46% to 100.04%, respectively, which met the predetermined criteria for pharmacokinetic equivalence. Despite the single administration, significant changes in maximal blood pressure and heart rate were observed after drug administration for both formulations, compared with baseline values (all, P < 0.001). However, no significant differences were observed between the 2 formulations in terms of pharmacodynamic profiles, and no clinically relevant changes were observed for either formulation with respect to physical examination, hematology, biochemistry, electrocardiography, or urinalysis. Neither formulation caused any serious adverse events.

CONCLUSIONS

Two amlodipine formulations were found to be equivalent in terms of the pharmacokinetics of S-amlodipine. The newly developed formulation, comprised of only S-amlodipine, had pharmacodynamic profiles comparable to those of the conventional racemic amlodipine formulation in these healthy Korean male subjects. Both formulations were well tolerated.

Relative bioavailability and pharmacokinetics of a new sibutramine formulation in healthy male subjects: a randomized, open-label, two-period, comparative crossover study

BACKGROUND

Sibutramine is an orally administered, centrally acting antiobesity drug. Sibutramine hydrochloride monohydrate is the conventional formulation, whereas sibutramine mesylate hemihydrate is a newly developed formulation. Drugs formed from different salts may differ in their solubility profiles and dissolution rates, which may affect their rate of absorption and thus their onset, duration, and intensity of effect.

OBJECTIVE

This study was conducted to compare the relative bioavailability and pharmacokinetics of the new sibutramine formulation (test) with those of the conventional formulation (reference).

METHODS

: This was a single-center, randomized, open-label, 2-period, comparative crossover study in healthy male subjects. All subjects received a single 15-mg oral dose of sibutramine hydrochloride monohydrate (reference) and a single 17.3-mg oral dose of sibutramine mesylate hemihydrate (test), both containing 12.55 mg sibutramine base. The 2 doses were separated by a 2-week washout period. Blood samples for pharmacokinetic analysis were collected during a 72-hour period after treatment. Safety parameters were assessed, including adverse events, hematology and biochemistry, urinalysis, and electrocardiography. Plasma concentrations of the active metabolites of sibutramine (desmethylsibutramine [M1] and didesmethylsibutramine [M2]) were determined, and the pharmacokinetic characteristics of the 2 formulations were compared using noncompartmental analysis.

RESULTS

Sixteen subjects (mean [SD] age, 24.3 [2.3] years [range, 20-25 years]; mean [SD] body weight, 66.1 [5.1] kg [range, 57-77 kg]) were enrolled in and completed the study. The plasma concentration-time profiles of M1 and M2 were similar after administration of both formulations. The reference and test formulations showed pharmacokinetic equivalence with respect to M1 and M2. The relative bioavailability of the test drug was 117.6% for M1 and 102.4% for M2. The 90% Cls for the ratios of the log-transformed C(max) and AUC values were within the predetermined equivalence range of 80% to 125%. There were no significant changes in physical, biochemical, hematologic, or urinalysis variables during the study. Neither formulation was associated with any serious adverse events.

CONCLUSION

In this study in healthy male subjects, the 2 sibutramine formulations were pharmacokinetically equivalent, and the newly developed formulation had a safety profile comparable to that of the conventional formulation.

Randomized, open-label, two-period crossover comparison of the pharmacokinetic and pharmacodynamic properties of two amlodipine formulations in healthy adult male Korean subjects

BACKGROUND

Amlodipine, a third-generation dihydropyridine calcium antagonist, is prescribed in the management of angina and hypertension. A newly developed amlodipine formulation (amlodipine camsylate) is associated with similar physical properties, melting point, and solubility-and improved stability against long-term stability test and accelerated temperature test-compared with the conventional formulation (amlodipine besylate).

OBJECTIVE

This study was performed to compare the pharmacokinetic (PK) and pharmacodynamic (PD) properties and safety profiles of a newly developed amlodipine formulation with a conventional formulation in healthy male subjects.

METHODS

This randomized, open-label, 2-period crossover comparative study was conducted at the Clinical Trial Center, Gil Medical Center, Gachon Medical School (Incheon, Korea). Eighteen healthy male Korean subjects aged 20 to 40 years were enrolled. All subjects received a single oral dose (5-mg tablet) of a conventional (reference) or newly developed (test) amlodipine formulation. Blood samples for PK analysis of amlodipine were obtained during the 144-hour period after dosing. Systolic and diastolic blood pressure (BP) (SBP and DBP, respectively) and pulse rate (PR) were measured just before each blood sampling. Assessment of safety profiles, including hematology and biochemistry, electrocardiography, urinalysis, and monitoring of adverse events (AEs), was performed.

RESULTS

All participants completed both treatment periods. Their mean (SD) age was 22.3 (1.5) years (range, 20-25 years) and their mean (SD) body weight was 67.9 (5.6) kg (range, 57-77 kg). The plasma concentration-time profiles of amlodipine were similar after administration of the 2 formulations. The reference and test formulations were pharmacokinetically equivalent. The 90% CIs for the mean treatment ratios of the log-transformed peak plasma concentration and the area under the plasma concentration-time curve were within the predetermined equivalence range of 80% to 125%. Despite administration of a single dose, significant maximal changes in SBP, DBP, and PR were achieved after drug administration for both formulations compared with baseline values (all, P < 0.001). No significant differences in PD profiles were found between the 2 formulations. No clinically relevant changes were observed in physical, biochemical, hematologic, electrocardiographic, or urinalysis findings during the study. Neither formulation caused any AEs during the study.

CONCLUSIONS

The 2 amlodipine formulations were pharmacokinetically equivalent and showed similar PD characteristics in these healthy male subjects.

Bioavailability of immediate and controlled release formulations of lithium carbonate

INTRODUCTION/OBJECTIVES: Controlled-release lithium formulations were developed to minimize elevated blood peaks, related to side-effects and intoxications. However, there is little information about the bioavailability of the only controlled-release lithium formulation available in Brazil. The objective of this study was to compare the bioavailability of controlled-release and immediate-release lithium formulations, after single and multiple doses. METHODS: Twelve healthy volunteers received 900 mg of immediate-release or controlled-release lithium carbonate in single or multiple doses during 9 days. After single dose administration, the following parameters were analyzed for each formulation: maximum lithium concentration (Cmax); time to reach Cmax (t max); area under the curve of serum concentration versus time (AUC0-12 and AUC0-<FONT FACE=Symbol>¥</FONT>) and the elimination half-life (t1/2 elim.). After multiple doses, Cmax; t max; AUC0-12; mean (Cmean) and minimum drug concentration (Cmin) and degree of fluctuation (DF) were analyzed. A 90% confidence interval (90%CI) for the ratio between the AUCs for each formulation was constructed. RESULTS/DISCUSSION: Following single dose, the two formulations were bioequivalent; however, they were not after multiple doses. This fact could be a consequence of methodological limitations of lithium level's measurements since, following single dose, these levels could not be detected at time periods 24 and 48h in many volunteers, compromising the calculation of t1/2 elim ,and consequently of the AUC0<FONT FACE=Symbol>-¥</FONT> and the 90%CI to the ratio of these areas. Therefore, the bioequivalence found after single dose may be an unreliable result.

Bioequivalent or nonbioequivalent?

The current tests for bioequivalence are based on assumptions that are not valid in general; this paper shows why it is necessary to use a method that does not depend upon assumptions that cannot, and need not, be proved in general.