The Safety and Pharmacokinetics of Carprofen, Flunixin and Phenylbutazone in the Cape Vulture (Gyps coprotheres) following Oral Exposure

The following study evaluates the overt toxic potential of carprofen (CRP), flunixin (FXN) and phenylbutazone (PBZ) in Old world vultures in relation to historic toxicity data for diclofenac and ketoprofen, with the Cape vulture (Gyps coprotheres) being the indicator species. The toxic potential of a single oral dose of CRP (11.5 mg/kg), FXN (1 mg/kg), PBZ (1.7 mg/kg) or water was evaluated by means of a four-way parallel study (n = 2), as means of ascertaining if these drugs were as toxic as diclofenac in the vulture. No unscheduled deaths or pathological lesions were noted following exposure. Clinical signs of lethargy and depression were, however, noted in one CRP, two FXN and one PBZ treated birds. Mild reversible inhibition of UA excretion was evident in all three groups, although UA remained within the population reference interval in contrast to the effects previously described for diclofenac and ketoprofen. All treatment groups had a drug concentration responsive increase in alanine transferase activity. CRP, FXN and PBZ were characterised by a maximum plasma concentration (Cmax) of 1051.8 +/- 620.7 ng/ml, 335.9 +/- 36.3 ng/ml and 11150 +/- 2474.9 ng/ml at 4 +/- 4.3, 0.45 +/- 0.02 and 5.3 +/- 5.2 hours (Tmax) respectively and a half-life of elimination of 13.3 +/- 5, 1.8 +/- 1 and 18.7 +/- 11.4 hours respectively. While we could not demonstrate a lethal effect of the tested substances, the presence of toxic clinical signs, clinical pathological changes and/or long half-lives of elimination suggests that all three drugs have a potential for toxicity in a larger population or on repeat administration. In conclusion while the studied substances were not as overtly toxic as diclofenac, they are of safety concern.