Pharmacokinetics and absolute bioavailability of lansoprazole

In a crossover study 12 healthy volunteers received lansoprazole 15 mg or 30 mg orally, or 15 mg intravenously in randomized order as a single dose. Blood samples were taken and plasma levels of lansoprazole were determined using an HPLC method. The volunteers were phenotyped for the debrisoquine/sparteine and mephenytoin polymorphisms.

The total clearance was 517 ml.min-1, and the absolute bioavailability was 91% for the 30-mg and 81% for the 15-mg enteric-coated formulation. The elimination half-life was about 1 h. No correlation of the plasma levels to the sparteine metabolic ratio was found, and no correlation to the mephenytoin type could be established, since all volunteers of the mephenytoin type were extensive metabolizers. Although considerable variation, inter- and intraindividually, was observed, the increase in Cmax and AUC did not deviate from dose proportionality. The present galenic formulation ensures a high bioavailability after a single dose.