Metronidazole vs Diet Alone for Treatment of Acute Colitis in Dogs

In the Literature 

Rudinsky AJ, Parker VJ, Winston J, et al. Randomized controlled trial demonstrates nutritional management is superior to metronidazole for treatment of acute colitis in dogs. J Am Vet Med Assoc. 2022;260(S3):S23-S32. doi:10.2460/javma.22.08.0349  

The Research … 

Acute colitis is often managed empirically. Metronidazole is commonly prescribed in patients with acute colitis in the absence of definitive diagnosis or known optimal treatment, despite the relative infrequency of infectious acute colitis and limited evidence for efficacy of this therapy.^1,2 Metronidazole does not improve recovery compared with other treatments and negatively impacts the gut microbiome, contributing to dysbiosis, antibiotic-associated diarrhea, negatively altered metabolism, and delayed recovery.^3-11 Enteral nutrition is important to maintain intestinal barrier function, control inflammation, and support the gut microbiome and may be an antibiotic-sparing therapy.  

This randomized, placebo-controlled clinical trial* investigated the effectiveness of exclusively feeding a purpose-formulated, easily digestible kibble for 30 days to otherwise healthy dogs presented for uncomplicated, acute (ie, <3 days), nonparasitic colitis with or without concurrent 7- to 10-day treatment with metronidazole (5-10 mg/kg PO every 12 hours). Dogs were randomized into groups to receive diet and placebo, diet and metronidazole, or a psyllium-fiber–enhanced version of the diet and placebo.  

In the 59 dogs that completed the study, metronidazole delayed remission significantly (mean, 9.3 days; range, 7-12 days) and caused a marked negative shift in the dysbiosis index at days 7 to 10. Dogs receiving diet with placebo and psyllium-enhanced diet with placebo achieved remission significantly earlier (mean, 6 days and 4.8 days, respectively). Differences between the placebo groups were not statistically significant; however, the psyllium-enhanced diet with placebo group averaged fewer relapses (0.65) with none past day 9, compared with an average of 1.68 relapses occurring up to day 17 in the diet with placebo group. Dogs in the diet with metronidazole group had an average of 1.3 relapses up to day 23.  

In this study, outcomes were better with diet alone. Metronidazole hindered recovery and negatively affected the gut microbiome compared with diet alone, but all dogs clinically recovered.  

Easily digestible diets are readily available and practical to feed. Dietary fiber supplementation is often beneficial for patients with chronic colitis. Psyllium husk fiber can increase viscosity of liquids, bind certain toxins, and support microbial balance and colonocyte function. Whether fiber supplementation provides significant additional benefit for treatment of acute colitis is uncertain; however, ability to minimize relapses or longer-term effects is clinically relevant and warrants further study. Fecal microbial transplant is the only other intervention documented to improve the outcome of clinical signs and the microbiome.⁵

… The Takeaways 

Key pearls to put into practice: 

• Dietary management alone more effectively and safely treats noninfectious acute colitis than in combination with metronidazole administration. Empiric management with an easily digestible or psyllium-fiber–enhanced kibble more effectively resolves clinical signs and avoids the potential negative effects of metronidazole.  

• Metronidazole is unnecessary and detrimental in noninfectious cases of acute colitis. Anti-inflammatory effects of this drug are not documented in dogs, and use can worsen dysbiosis (potentially permanently) and delay recovery. Avoiding indiscriminate empiric use supports antimicrobial stewardship and prevents other potential adverse effects (eg, stress associated with administration; antibiotic-associated anorexia, nausea, or diarrhea; serious toxicoses or overdoses).   

• Infectious acute colitis cases are less common than noninfectious cases and are often parasitic. Centrifugal fecal flotation and Giardia spp/Cryptosporidium spp antigen testing are readily available for screening, and empiric treatment with fenbendazole provides broader-spectrum antiparasitic activity than metronidazole with minimal impact on the gut microbiome.¹¹ 

*This study received funding from Royal Canin.