Metronidazole treatment of acute diarrhea in dogs: A randomized double blinded placebo‐controlled clinical trial

Background Metronidazole is commonly administered to dogs with acute diarrhea, but there is limited evidence to support this practice. Objective To investigate the effects of metronidazole administration on dogs with acute nonspecific diarrhea. Animals Thirty‐one dogs, including 14 test population dogs and 17 controls. Methods Randomized controlled clinical trial. Dogs with acute diarrhea in which causation was not determined by routine fecal diagnostic testing were randomly assigned to metronidazole treatment (10‐15 mg/kg PO q12h for 7 days) or placebo. Fecal cultures and characterization of Clostridium perfringens isolates also were performed. Owners maintained medication and fecal scoring logs, and fecal diagnostic tests were repeated on day 7. Results The mean ± SD time to resolution of diarrhea for test population dogs (2.1 ± 1.6 days) was less than that for controls (3.6 ± 2.1 days, P = .04). Potential relationships of C. perfringens with acute diarrhea pathogenesis were not investigated, but only 3 of 13 (23.1%) test population dogs had persistent C. perfringens carriage at day 7, which was less than the 11 of 14 (78.6%) controls with persistent growth (P = .007). Conclusions and Clinical Importance Our results suggest that metronidazole treatment can shorten duration of diarrhea and decrease fecal culture detection of C. perfringens in some dogs with acute nonspecific diarrhea. Additional studies are needed to assess the benefits and risks of routine use of metronidazole for this purpose because most dogs achieve resolution of diarrhea within several days regardless of treatment.