Meseclazone (W2395;NSC297623) exhibits inhibitory potency of secondary phase ADP aggregation. Meseclazone possesses anti-inflammatory, analgesic and antipyretic activity. In Vivo: Meseclazone inhibits collagen-induced aggregation 1 and 4 hr after oral administration^[1]. Intravenous administration of Meseclazone and other nonsteroidal anti-inflammatory drugs caused a dose-dependent inhibition of bronchoconstriction resulting in the following order of descending potency: isoproterenol congruent to indomethacin greater than fenoprofen greater than tolmetin greater than aspirin greater than naproxen congruent to ibuprofen greater than phenylbutazone greater than diflunisal greater than Meseclazone greater than 5-CSA^[2].