Inhibition of ADP-induced platelet aggregation by dipyrone in patients with acute myocardial infarction.

ADP induced platelet aggregation was investigated in 48 patients within three days of the first signs of acute myocardial (AMI). Thirty six of them received 1 gram of dipyrone. Twelve patients who did not receive dipyrone served as controls. Platelet aggregation was found severely inhibited in 11 patients who had received dipyrone up to 12 hours before investigation and moderately inhibited among 25 patients who were given the drug 12-24 hours prior to the investigation. All the patients with AMI who did not receive dipyrone, exhibited a state of hyperaggregability evidenced by the presence of a second phase of aggregation even with 0.5 microM ADP. The inhibitory activity of dipyrone on the second phase of platelet aggregation resembles that of other non steroidal anti-inflammatory drugs.