Minimal Interaction between Gatifloxacin and Oxycodone

Previous studies have demonstrated a significant reduction in the oral bioavailability of trovafloxacin and ciprofloxacin when administered concomitantly with an intravenous opiate, such as morphine. This decrease in absorption results in a 36% and 50% lower AUC for trovafloxacin and ciprofloxacin, respectively, which could cause clinical failures. The authors investigated the possibility of a similar interaction between oxycodone and gatifloxacin. Twelve healthy volunteers were randomized in an open-label, two-way crossover study to receive oxycodone (5 mgpo Q4H) andgatifloxacin (400 mg po 1 h) after starting the oxycodone or gatifloxacin 400 mg po alone. Blood samples were drawn at 0, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 18, and 24 hours postdosing. No significant difference was noted (p > 0.05) in AUC (31.6 +/- 7.3 vs. 31.7 +/- 7.1) and Cmax (3.2 +/- 0.6 vs. 3.0 +/- 0.6) for gatifloxacin versus gatifloxacin/oxycodone regimens; however, the tmax (1.8 +/- 0.8 vs. 4.3 +/- 1.5) was significantly delayed (p < 0.001). It was concluded that oral oxycodone and gatifloxacin can be administered concomitantly without a significant decrease in bioavailability.