The goal of this study was to develop a paw inflammation model that could be used in evaluating nonsteroidal antiinflammatory drugs (NSAIDs). The investigators found that SC injection of 500 mg of kaolin into a paw caused an acute inflammatory response that lasted 5 to 10 days. Increases in body temperature, skin temperature, and paw volume confirmed the clinical assessment that the paw was painful. The cats had reduced weight-bearing on the injected limb and exhibited guarded movement of the paw. Doses of kaolin above 500 mg resulted in necrosis of the skin, whereas doses below 500 mg did not produce an inflammatory response that was prolonged enough for the drugs to be evaluated. The suitability of this model for future testing of NSAIDs was confirmed via pilot studies in which several kaolin-injected cats were treated with meloxicam and tolfenamic acid and assessed for lameness and pain. In this study, kaolin produced a reproducible model of inflammation with measurable variables suitable for evaluating NSAIDs in cats.

COMMENTARY: Few appropriate animal models for inflammation exist in veterinary patients for accurate preclinical evaluation of pharmacologic profiles of NSAIDs. Thus, when drugs are marketed, the practicing veterinarian often discovers the real effects of the drugs in patients. The authors of this paper report the development of an appropriate model in the cat (SC injection of kaolin in the paw) that provides a useful model of inflammation and pain in the cat. I hope that more such models will be developed to give veterinarians a better indication of what these drugs do, and that continued research in this area will lead to increased options for safe pain management in cats.

Development and validation of a new model of inflammation in the cat and selection of surrogate endpoints for testing antiinflammatory drugs. Giraudel JM, Diquelou A, Lees P. PHARMACOL THER 28:275-285, 2005.