Effects of metronidazole on hepatic CYP3A4 activity

Study Objective. To evaluate the effect of a short course of oral metronidazole, commonly used for bowel-preparation regimens, on hepatic cytochrome P450 (CYP) 3A4 activity, as measured by the [¹⁴C N-methyl]-erythromycin breath test (ERMBT) in healthy volunteers. Design. Prospective, nonrandomized, interventional study. Setting. University-affiliated, community, teaching hospital. Subjects. Five healthy male volunteers. Intervention. Subjects underwent a baseline ERMBT in the morning before receiving three oral doses of metronidazole 500 mg administered at 3 P.M., 7 PM., and 11 PM. Repeat ERMBTs were performed at 24, 72, and 96 hours after the initial ERMBT. Changes in ERMBT values were compared with baseline results using Freidman's repeated-measures analysis of variance on ranks. Measurements and Main Results. The ERMBT values did not change significantly compared with baseline (p=0.82). Median (range) ERMBT values expressed as a percentage of baseline at 24, 72, and 96 hours were 110.3 (96.2-136.9), 101.3 (99.3-115.0), and 101.8 (95.5-116.3), respectively. Conclusion. A short course of oral metronidazole does not result in a significant change in hepatic CYP3A4 activity as measured by the ERMBT.