EFFECTS OF SINGLE ORAL DOSES OF LYSINE CLONIXINATE AND ACETYLSALICYLIC-ACID ON PLATELET FUNCTIONS IN MAN

Lysine clonixinate is an analgesic drug with a so far unknown mechanis m of action. We have determined its effect on platelet cyclooxygenase in man. Biosynthesis of thromboxane (TX)B-2 and prostaglandin (PG)F-2 alpha in clotting whole blood ex vivo as well as collagen-induced plat elet aggregation measured before and at various time points after oral administration of 125 mg lysine clonixinate were compared to results obtained with 500 mg acetylsalicylic acid (ASA). While biosynthesis of both TXB(2) and PGF(2 alpha) measured radioimmunologically was inhibi ted significantly 2.5 h, but not 6 h, after administration of lysine c lonixinate, inhibition by ASA was much greater and still highly signif icant after 48 h. Similarly, collagen-induced aggregation of platelet- rich plasma was inhibited for a longer period and to a greater extent after administration of ASA than after lysine clonixinate. Our results indicate that lysine clonixinate is a cyclooxygenase inhibitor of mod erate potency. It remains to be investigated whether mechanisms other than inhibition of cyclooxygenase contribute to the analgesic activity of lysine clonixinate.