In vitro biopharmaceutical equivalence of carbamazepine sodium tablets available in Lima, Peru

Carbamazepine is an antiepileptic iminostilbene that is dispensed from multiple sources in Peru without bioequivalence studies. The biopharmaceutical equivalence of two generic (A and B) and one commercial brand (C) of carbamazepine sodium as compared to the innovator drug was determined by an in vitro study of commercial 200-mg tablets, following the guidelines of the Biopharmaceutical Classification System. Hardness, weight, friability, and content were evaluated for compliance with official specifications. A United States Pharmacopeia (USP) dissolution apparatus 2 (paddle) was used at with 900 mL of medium (pH 1.2, 4.5, and 6.8) at 75 rpm and 37 ± 0.5 °C. Samples (5 mL) were withdrawn at 5, 10, 15, 30, 45, 60, and 90 minutes and analyzed in a UV spectrophotometer at 288 nm. The studied drugs did not release 85% of the active pharmaceutical ingredient within 30 minutes in any media. When compared to the innovator brand using the similarity factor (f2), product A was < 50 at all three pH levels; B was < 50 at pH 4.5, and C was < 50 at pH 1.2 and 4.5. For all products, dissolution efficiency was 56.1–84.3% and mean dissolution time was 18.0–47.5 min. Despite meeting the official specifications for quality control tests, the evaluated samples are not in vitro biopharmaceutical equivalents with the innovator brand based on the dissolution profiles (f2 < 50).