Analytical Evaluation of Bioequivalence Data for Generic Antihypertensives Registered with NAFDAC

Generic substitution of branded antihypertensives is a cornerstone of Nigeria's affordability policy, yet the adequacy of bioequivalence documentation for NAFDAC-registered generic antihypertensives has not been systematically evaluated in the literature. This study conducted an analytical review of publicly accessible bioequivalence data for NAFDAC-registered generic antihypertensive medicines, focusing on amlodipine, lisinopril, and hydrochlorothiazide formulations. A retrospective documentary analysis methodology was employed, accessing the NAFDAC product registration database and supplementary literature sources to identify all registered generic antihypertensive products for the three drug classes. Bioequivalence documentation quality was assessed using the WHO Multisource Pharmaceutical Products Guidelines criteria, covering study design adequacy, pharmacokinetic parameter reporting, and acceptance criteria application. A total of 87 generic products were included in the analysis. Full bioequivalence documentation meeting WHO standards was confirmed for 54.0 percent of reviewed products. For the remainder, documentation was absent from publicly accessible sources or failed to report sufficient pharmacokinetic parameters for independent assessment. Amlodipine generic products showed the highest documentation completeness rate (68.4 percent), while lisinopril products had the lowest (44.8 percent). The study identifies a significant evidence gap regarding the bioequivalence assurance for a substantial proportion of generic antihypertensives prescribed in Nigeria, and recommends NAFDAC strengthen its documentation transparency requirements and consider mandatory post-registration bioequivalence verification for commonly prescribed generics.

Keywords: bioequivalence, generic antihypertensives, NAFDAC, bioavailability, pharmaceutical quality