Bioavaibility of ranitidine tablets commercially available in Thailand

Abstract

Five brands of 150 mg ranitidine tablets commercially available in Thailand were evaluated. In vitro studies showed that all products met the requirement of the British Pharmacopoeia 1980 for disintegration time. Dissolutions of tablets were different in acidic medium (p < 0.05). However, no statistically significant differences (p > 0.05) in dissolution characteristics were observed in basic medium. After doses of 50 mg intravenously and two 150 mg orally, ranitidine kinetics and bioavailability were investigated using a single dose crossover study in 12 Thai normal volunteers. Plasma concentrations of ranitidine were determined using high-performance liquid chromatographic method. Individual plasma profile was analyzed according to noncompartmental analysis. There were no statistically significant differences (p > 0.05) in relevant parameters studied among the five brands except only the AUC values. The mean peak plasma levels were 2.05 ± 0.42 mcg/ml and 1.19 ± 0.17 mcg/ml following intravenous and oral administration, respectively. The average time to peak were ranged from 0.5-3.0 hours. The biological half life was 1.44 ± 0.24 hours. The absolute bioavailabilities were ranged from 42.27 ± 12.44 to 67.24 ± 13.24% and the relative bioavailabilities of ranitidine tablets for brands B, C, D and E with respect to brand A were 97.36, 91.09, 94.33 and 144.00%, respectively. It was also shown that the dissolution rate of the drug in acidic medium is correlated to tmax (p < 0.05). No statistically significant linear relationships were observed among other parameters (p > 0.05). The studies indicate that all ranitidine tablets commercially available in Thailand are bioequivalent.