Randomized, controlled, crossover trial of prevention of antibiotic-induced gastrointestinal signs using a synbiotic mixture in healthy research dogs.

backgroundSynbiotics decrease antibiotic-associated gastrointestinal signs (AAGS) in cats, but data supporting synbiotic use to ameliorate AAGS in dogs are lacking.

objectivesTo determine if administration of synbiotics mitigates AAGS in dogs. ANIMALS: Twenty-two healthy research dogs.

methodsRandomized, double-blinded, placebo-controlled, 2-way, 2-period, crossover study with an 8-week washout period. Each period included a 1-week baseline and 3-week treatment phase. Dogs received enrofloxacin (10 mg/kg PO q24h) and metronidazole (12.5 mg/kg PO q12h), followed 1 hour later by a bacterial/yeast synbiotic combination or placebo. Food intake, vomiting, and fecal score were compared using repeated-measures crossover analyses, with P < .05 considered significant.

resultsHyporexia, vomiting, and diarrhea occurred in 41% (95% confidence interval [CI], 21-64), 77% (95% CI, 55-92), and 100% (95% CI, 85-100) of dogs, respectively, during the first treatment period. Derangements in food intake were smaller in both periods for dogs receiving synbiotics (F-value, 5.1; P = .04) with treatment-by-period interactions (F-value, 6.0; P = .02). Days of vomiting differed over time (F-value, 4.7; P = .006). Fecal scores increased over time (F-value, 33.5; P < .001), were lower during period 2 (F-value, 14.5; P = .001), and had treatment-by-period effects (F-value, 4.8; P = .04). CONCLUSIONS AND CLINICAL IMPORTANCE: Enrofloxacin/metronidazole administration is associated with a high frequency of AAGS. Synbiotic administration decreases food intake derangements. The presence of milder AAGS in period 2 suggests that clinical effects of synbiotics persist >9 weeks after discontinuation, mitigating AAGS in dogs being treated with antibiotics followed by placebo.