Veterinary homeopathy: systematic review of medical conditions studied by randomised placebo-controlled trials

A systematic review of randomised controlled trials (RCTs) of veterinary homeopathy has not previously been undertaken. Using Cochrane methods, this review aims to assess risk of bias and to quantify the effect size of homeopathic intervention compared with placebo for each eligible peer-reviewed trial. Judgement in seven assessment domains enabled a trial's risk of bias to be designated as low, unclear or high. A trial was judged to comprise reliable evidence if its risk of bias was low or was unclear in specified domains. A trial was considered to be free of vested interest if it was not funded by a homeopathic pharmacy. The 18 eligible RCTs were disparate in nature, representing four species and 11 different medical conditions. Reliable evidence, free from vested interest, was identified in two trials: homeopathic Coli had a prophylactic effect on porcine diarrhoea (odds ratio 3.89, 95 per cent confidence interval [CI], 1.19 to 12.68, P=0.02); and individualised homeopathic treatment did not have a more beneficial effect on bovine mastitis than placebo intervention (standardised mean difference -0.31, 95 per cent CI, -0.97 to 0.34, P=0.35). Mixed findings from the only two placebo-controlled RCTs that had suitably reliable evidence precluded generalisable conclusions about the efficacy of any particular homeopathic medicine or the impact of individualised homeopathic intervention on any given medical condition in animals.