Pharmacolog/ca/ Research Cornmun/cat/ons, Vol. 13, No. 9, !98 ! 847 INDOBUFEN TREATMENT IN TYPE IIA HYPERCHOLESTEROLEMIC SUBJECTS: EFFECTS ON PLATELET FUNCTION AND MALONDIALDEHYDE PRODUCTION E. Tremoli, P. Maderna, M. Sirtori, S. Colli, G. Corvi ° and C.R. Sirtori E. Crossi Paoletti Center, Institute of Pharmacology and Pharmacognosy, University of Milan, Milan, Italy Received in final form 3 June 1981 SUMMARY Indobufen, an inhibitor of platelet aggregation, or a matchin K placebo were administered (200 mE b.i.d, by oral route) to 8 hypercholesterolemic subjects and to 8 normal volunteers, according to a randomized cross-over design for three days with a four day interval. Platelet aggregation and malondialdehyde (MDA) production by plate- lets were measured before and during treatment. Indobufen administration completely suppressed the aggregation of platelets induced by threshold concen- trations of arachidonic acid, as well as the second wave of aggregation induced by epinephrine, up to twelve hours from drug treatment. MDA production was also completely suppressed by Indobufen administration. Platelets from type IIA patients needed lower concentrations of a~regat- inE agents, to overcome the inhibitory effect of Indobufen. INTRODUCTION An increased incidence of arterial thrombosis and of peripheral vascular disease, in patients with type IIA o present address: Farmitalia Carlo Erba, Milan, Italy. 0031-6989/81/090847-13/$02,00/0 E>1981 The Italian Pharmacological Society