Abstract:The objective of the present study was test the anti-inflammatory efficacy of diclofenac dietilamine, applied epicutaneously at a dose rate of 0.44 mg kg 1 , in a model of acute arthritis in horses. Four clinical end-points, as well as two biochemical markers, were used as surrogate markers of the required clinical response (analgesia, anti-inflammatory). Low diclofenac concentrations were measured in blood (C max 0.04±0.03 ug mL 1 ) and synovial fluid (C max 0.08 ±0.08 ug mL 1 ) from the first to the last sampling time. The statistical comparison of the clinical end-points and biochemical markers between placebo and dicilofenac treated group indicated a lack of pharmacological effect of this compound after epicutaneous administration.