Effect of acid secretion blockade by omeprazole on the relative bioavailability of orally administered furazolidone in healthy volunteers

Aims The administration of omeprazole may interfere with the absorption of orally administered drugs by reducing gastric pH and hence tablet dissoluti on. The aim of this study was to investigate the effects of a 5 day adminis tration of omeprazole on the pharmacokinetics of furazolidone. Methods Eighteen healthy (nine male and nine female) volunteers were select ed. The study had an open randomized two-period crossover design with a 21 day washout period between the phases. Serum concentrations of furazolidone were measured by reversed-phase h.p.l.c. with ultraviolet detection. Results Administration of omeprazole caused a significant reduction of C-ma x [0.34 mug ml(-1) (range 0.25-0.43) vs 0.24 mug ml(-1) (range 0.15-0.34)] with no significant delay in absorption t(max) [2.5 h (range 1.85-3.0) vs 2 .4 h (range 2.06-2.71)]. Conclusions Furazolidone was rapidly absorbed after oral administration. Sh ort-term treatment with omeprazole did alter the relative bioavailability o f this drug, probably through an effect on absorption kinetics or first-pas s metabolism.