Clinical efficacy of 12-h metronidazole dosing regimens in patients with anaerobic or mixed anaerobic infections.

Traditional metronidazole dosing regimens utilize an every 8 h dosing strategy to treat anaerobic and mixed anaerobic infections. However, pharmacokinetic data demonstrate that the half-life of metronidazole is 8-12 h and blood levels at 12 h exceed the in vitro minimum inhibitory concentration (MIC) for most anaerobic infections. The primary objective of this study was to evaluate the frequency of clinical cure among patients who received metronidazole every 12 h compared with those who received an every 8 h frequency. Secondary endpoints included duration of antibiotics, hospital length of stay, escalation of antibiotic therapy, microbiologic cure, and mortality.

Methods: This retrospective, single-center, pre-post intervention study of 200 patients between June 2014 to July 2016.

Results: No significant differences in clinical cure for every 12 h versus every 8 h metronidazole dosing regimens (85% for both groups, p = 1.00) were found. There were no differences in any of the secondary endpoints, with a mean duration of antibiotic therapy being 5.9 versus 5.8 days and a hospital length of stay averaging 8.1 versus 6.7 days for the 12- and 8-h dosing groups, respectively ( p > 0.05).

Discussion: Findings validate pharmacokinetic data suggesting that an extended metronidazole dosing interval effectively treats anaerobic infections.