Bioequivalence Study of Sildenafil 20 mg Tablets in Healthy Thai Male VolunteersB. Chuasuwan*, P. Ratnatilaka Na Bhuket, W. Supasena, C. Manamuti, I. Techatanawat, P. Narakorn, A. Rojanawiwat, and A. Eksaengsri
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The present study aims to evaluate the bioequivalence of the generic formulation, sildenafil GPO 20 mg tablets to the originator, Revatio® 20 mg tablets. The study was a randomized, single dose, two-way, cross-over, open-label study which included 32 healthy Thai male volunteers under fasting conditions with a 7-day washout period. After drug administration, blood samples have been collected at the predefined time points and the plasma concentrations of sildenafil and its metabolite, piperazine N-desmethylsildenafil, were analyzed using validated LC-MS/MS method. The pharmacokinetic parameters assessed were area under the plasma concentration time curve from time 0 hour to 24 hours (AUC0-24), AUC from time zero to infinity (AUC0-∞), the peak plasma concentration (Cmax), and time to achieve the Cmax (tmax). The geometric mean (90% CI) values for the ratio of AUC0-24, AUC0-∞ and Cmax of the test product over those of the reference product were 101.0% (92.0-110.9%), 100.8% (92.1-110.4%) and 100.9% (90.0-113.1%) for sildenafil, respectively. The geometric mean ratios (90% CI) for piperazine N-desmethylsildenafil were 100.6% (95.1-106.4%), 99.8% (95.2-104.6%), and 100.8% (92.0-110.3%) for AUC0-24, AUC0-∞ Cmax, respectively. The differences between the test and reference product in tmax values were not statistically significant (P>0.05). The 90% confidence intervals of the test/reference AUC ratio and Cmax ratio of sildenafil and piperazine N-desmethylsildenafil were within the acceptance range for bioequivalence. There was no adverse event observed during this bioequivalence study. Both formulations were equivalent in terms of extent and rate of absorption.
Keyword:
Pulmonary arterial hypertension, Phosphodiesterase-5 inhibitor, Bioequivalence, Sildenafil, Pharmacokinetics
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