Comparison of absorption rate and bioavailability of two brands of carbamazepine.

OBJECTIVE: To assess the bioavailability of carbamazepine from two brands of carbamazepine--Tegretol 200 and Zen-200. METHODS: A two-way randomised cross-over bioavailability of carbamazepine was carried out in twelve healthy male volunteers. Coded plasma samples were analysed for levels of carbamazepine by high performance liquid chromatography (HPLC) method. Tegretol 200 and Zen-200 were tested for in-vitro dissolution profiles. RESULTS: The mean Cmax, Tmax and t1/2a for Tegretol 200 were: 2.17 +/- 0.42 mcg/mL, 11.67 +/- 6.37 h and 2.72 +/- 1.87 h; for Zen-200 were 3.10 +/- 0.05 mcg/mL, 3.50 +/- 2.11 h and 0.76 +/- 0.76 h respectively. These values were statistically significant. However AUC (0-96 h) value of 150.16 +/- 27.13 mcg/ml.h after Zen-200 was not statistically significant as compared to 128.68 +/- 20.22 mcg/ml.h after Tegretol 200. The in-vitro dissolution profiles of the two formulations were dissimilar. The fluctuations in CBZ levels after Tegretol 200 was significantly less as compared to Zen-200. The absorption profile as judged by parameter 'A' was 50.44 +/- 10.95 for Tegretol 200 and 42.49 +/- 18.89 for Zen-200. CONCLUSION: Based on parameter 'A' and other pharmacokinetic parameters, the marketed generic carbamazepine product, Zen-200 is not bioequivalent to Tegretol 200.