Background: Amlodipine is a dihydropyridine calcium channel antagonist that is useful in the treatment of hypertension and angina pectoris. In addition to the innovator brand of this molecule, several generic brands are marketed in Nigeria.
Objective: To evaluate the physicochemical equivalence of eight brands of amlodipine tablets marketed in Lagos, Nigeria.
Methods: Physicochemical properties such as identity, weight uniformity, friability, hardness test, disintegration test, dissolution test and assay of active ingredients were performed using the methods described in the British and the United States Pharmacopoeia. Ultra-violet spectrophotometric and High performance liquid chromatographic methods were used for assay of the labelled amount of amlodipine in the products.
Results: All the products passed weight uniformity and disintegration tests. Only one brand failed the friability test. Two brands had mean crushing strength less than 4 kg/cm²; while only 4 brands passed dissolution test by releasing >75% of the labelled amlodipine within 45 minutes. One brand failed both assay and dissolution tests by returning less than official specifications in the general monograph for conventional tablets. In all, four of the eight sample products analyzed passed all the tests. These can be said to be physicochemically equivalent and may be clinically interchangeable or substituted.
Conclusion: This study further highlights the concerns over the quality of drug products marketed in a developing country.