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

Abstract

Aims: The administration of omeprazole may interfere with the absorption of orally administered drugs by reducing gastric pH and hence tablet dissolution. The aim of this study was to investigate the effects of a 5 day administration of omeprazole on the pharmacokinetics of furazolidone.

Methods: Eighteen healthy (nine male and nine female) volunteers were selected. 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 Cmax [0.34 microg x ml(-1) (range 0.25-0.43) vs 0.24 microg x ml(-1) (range 0.15-0.34)] with no significant delay in absorption tmax [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. Short-term treatment with omeprazole did alter the relative bioavailability of this drug, probably through an effect on absorption kinetics or first-pass metabolism.

Figure 1

Serum furazolidone vs time curves (mean ± s.e.mean) obtained in serum of healthy volunteers after the oral administration of 200 mg of furazolidone in the presence (•), and absence of omeprazole (○).