The effect of coadministration of omeprazole on the bioavailability of oral garenoxacin was evaluated in an open-label study in 14 healthy subjects. Single-dose pharmacokinetics of garenoxacin were determined with and without steady-state omeprazole. Following an oral dose of garenoxacin 600 mg on day 1, serial blood samples were obtained over the next 72 hours. Omeprazole 40 mg once daily was administered from days 4 to 10. A second pharmacokinetic assessment of garenoxacin was conducted on day 8. Geometric means for the maximum observed concentration and area under the concentration-time curve from time 0 extrapolated to infinity were 9.6 microg/mL (18.2%) and 132.0 microg.h/mL (18.9%), respectively, for garenoxacin alone and 9.3 microg/mL (21.6%) and 140.4 microg.h/mL (22.1%), respectively, for coadministered garenoxacin and omeprazole. The 90% confidence interval for the ratio of geometric means (with/without omeprazole) for both variables was contained within 0.80 to 1.25, and the bioavailability of garenoxacin was not affected by the concomitant administration of omeprazole.