Formulation and bioequivalence of two sildenafil 50 mg film-coated tablets after a single oral administration

Objective: The aims of this study were to establish a bioanalytical method and to evaluate the bioequivalence of two drug products; a generic sildenafil 50 mg film-coated vs. the brand drug Viagra (R) 50 mg film-coated tablets. Method: Bioequivalence of tablets was tested by comparisons against the reference brand product in accordance with the requirements of the Declaration of Helsinki, the current Good Clinical Practice (GCP) Guidelines and the International Conference Harmonization (ICH). Results: The relationship between concentration and peak area ratio was found to be linear within the range of 1.435 - 410.023 ng/mL for sildenafil. The correlation coefficient (r) was always greater than 0.99 during the course of the validation. Statistical comparison of the main pharmacokinetic parameters showed no significant difference between test and reference. The 90% CIs of geometric mean ratios (test to reference ratios) were 99.656%, 99.806%, and 109.227% for AUC(0-last), AUC(0-infinity), and C-max, respectively. These pharmacokinetic parameter values lie within the FDA and European Medicines Agency specified bioequivalence limit (80 - 125%). Both formulations were well tolerated by all subjects and they were discharged in good health. Conclusion: The tested drug product was bioequivalent to the reference drug and had the same safety profile.