Droxicam, similar to piroxicam, inhibits in vivo renal synthesis of PGF2 alpha. This study was performed in rats; droxicam and piroxicam were administered orally at doses of 0.5, 1.2 and 8 mg/kg. Inhibitory activity of the two compounds was similar (40-60%) but showed no dose-effect relationship. Maximum inhibition was obtained with the 1 mg/kg dosage. In dogs droxicam has shown a clear inhibitory effect on arachidonic acid induced ex vivo platelet aggregation. Droxicam was administered orally at a dose of 2 mg/kg. Maximum inhibition (-40%) was achieved 24 hr post-administration and the effect was sustained up to 72 hr (-23%).