Effect of soybean administration on the pharmacokinetics of carbamazepine and omeprazole in rats.

Influence of soybean administration on the bioavailability of carbamazepine and omeprazole was studied after single dose administration of soybean (10 g/kg p.o.) or after chronic administration of soybean (50% w/w mixed with normal feed) for 15 days in rats. Carbamazepine was administered orally at a dose of 10 mg/kg and omeprazole at a dose of 20 mg/kg. Soybean decreased the bioavailability of carbamazepine after both single dose and chronic administration. It produced a significant decrease in C(max), T(max), AUC(0-t) of carbamazepine after single dose administration and increased the plasma clearance and V(d) along with decrease in C(max), T(max), AUC(0-t) and AUC(0-infinity) after chronic administration. On the contrary, soybean administration increased the bioavailability of omeprazole by producing an increase in C(max), AUC(0-t) and AUC(0-infinity) and a decrease in V(d) after single dose administration and a decrease in plasma clearance along with increase in C(max), AUC(0-t) and AUC(0-infinity) after chronic administration. The half-life of omeprazole was also increased after both acute and chronic administration of soybean. It was concluded that soybean decreases the bioavailability of carbamazepine and increases the bioavailability of omeprazole after both single dose and chronic administration.