Applications of equine models of acute inflammation. The Ciba-Geigy Prize for Research in Animal Health.
This review presents a brief historical prospective of the genesis of regulated medication in the US racing industry of which the non-steroidal anti-inflammatory drug phenylbutazone (PBZ) is the focus. It presents some historical guide posts in the development of the current rules on the use on PBZ by racing jurisdictions in the US. Based on its prevalent use, PBZ still remains a focus of attention. The review examines the information presented in a number of different models used to determine the effects and duration of PBZ in the horse. They include naturally occurring lameness and reversible induced lameness models that directly examine the effects and duration of the administration of various doses of PBZ. The review also examines indirect plasma and tissue models studying the suppression of the release of arachidonic acidderived mediators of inflammation. The majority of studies suggest an effect of PBZ at 24 hours at 4.4 mg/kg. This reflects and substantiates the opinion of many clinical veterinarians, many of whom will not perform a pre-purchase lameness examination unless the horse is shown to be free of NSAID. This remains the opinion of many Commission Veterinarians in that they wish to examine a horse pre-race without the possibility of a NSAID interfering with the examination and masking possible musculoskeletal conditions. Based on scientific studies, residual effects of PBZ remain at 24 hours following administration. The impact of sustained effect on the health and welfare of the horse and its contribution to injuries during competition remains problematic.