Bioavailability enhancement studies of amoxicillin with Nigella

Background & objectives: Nigella sativa Linn. is extensively used in the Indian diasporas as spice, which may interact with co-administered drugs and affect their intestinal availability. The purpose of this study was to investigate the effect of Nigella on bioavailability of amoxicillin in animal model. Methods: Everted rat intestinal sacs were used for in vitro experiment to study the transfer of amoxicillin across the gut. Amoxicillin (6 mg/ml) was co-infused with 3 and 6 mg of methanol and hexane extract of Nigella seeds separately. The amount of amoxicillin that traversed the gut was followed spectrophotometrically at 273 nm. For in vivo studies Wistar albino rats were used. Amoxicillin (25 mg/kg, po) was co-administered with hexane extract of Nigella seeds (25 mg/kg, po). The amount of amoxicillin in rat plasma was determined by UPLC-MS/MS method. Results: The in vitro studies both with methanol and hexane extracts of Nigella increased the permeation of amoxicillin significantly (P<0.001) as compared to control. Permeation was also found to be significantly higher for the hexane extract (P<0.001) in comparison to methanol extract at the same dose levels. In vivo experiments revealed that C-max of amoxicillin in rat plasma when administered orally alone and in combination with hexane extract increased correspondingly from 4138.251 +/- 156.93 to 5995.045 +/- 196.28 ng/ml while as AUC(0 -> t), increased from 8890.40 +/- 143.33 to 13483.46 +/- 152.45 ng/ml.h. Interpretation & conclusions: Nigella enhanced amoxicillin availability in both in vivo and in vitro studies. As the increase in bioavailability is attributed, in part, to enhanced diffusivity across intestine, our study indicated that Nigella increased intestinal absorption of amoxicillin.