Evaluation of In Vitro Equivalence of Commonly Available Generic Brands of Amlodipine Tablets in Saudi Arabia Under Biowaiver Conditions

Abstract

When a medicine is not able to treat the disease for which it was intended, as in case of substandard and falsified drug products, it may prolong the disease and in worst scenario, the patient may die because of the untreated illness or the product itself. To ensure the quality and safety of medicine, WHO recommends timely evaluation of pharmaceutical quality. The present study is an attempt to evaluate the pharmaceutical properties and in vitro drug release of four generic brands and one innovator product (Norvasc) of amlodipine tablets (5 mg) according to USP and WHO guidelines. The products passed the compendial specifications of weight variation (˂ 5% deviation), friability (˂ 1% weight loss), and assay (90–110% of labeled amount). The tablets were fast-disintegrating, as complete disintegration observed in 1.20–1.64 min. The dissolution profiles of the generic products were equivalent to the innovator brand in pH 1.2 HCl and acetate buffer (pH 4.5) without statistical treatment (≥ 85% release in 15 min). In phosphate buffer (pH 6.8), ≥ 85% of drug dissolved in 30 min and in vitro equivalence was established by calculating the difference factor (f1 ˂ 15), similarity factor (f2 ˃ 50), and dissolution efficiency (± 10%). The tested brands met WHO BCS-based biowaiver criteria for in vitro dissolution testing, which ensured their pharmaceutical and therapeutic equivalence without in vivo screening and interchangeability with the innovator product.