The effect of tiaprofenic acid and indomethacin administration of human platelet function

The present study compares the effects of two non-steroidal anti-inflammatory drugs (NSAIDs) on platelet function. Tiaprofenic acid (300 mg twice daily) and indomethacin (25 mg thrice daily) were administered to healthy volunteers for 6 days. Platelet aggregation and thromboxane A₂ (TXA₂) release (assessed as TXB₂, the stable, spontaneous breakdown product of TXA₂) were assessed before the adminstration of NSAIDs; on day 6 (2-3 h after the last dose of NSAID); and on days 7 and 8 (24 h and 48 h after the last dose of NSAID). Both tiaprofenic acid and indomethacin significantly inhibited platelet aggregation and TXA₂ release. The extent and duration of inhibition was similar for both drugs, and the inhibition tended to reverse within 24-48 h of cessation of medication. The time required for reversal of the inhbitiory effect of NSAIDs on platelets may be of relevance in patients who are bleeding (e.g. from gastric erosions caused by NSAIDs). Tiaprofenic acid in the present study and in previous work has not been shown to be a selective inhibitor of prostanoid synthesis, as was originally claimed.