Inhibition of primary ADP-induced platelet aggregation in normal subjects after administration of nitrofurantoin (furadantin).

The evidence indicating that platelets may play a role in the occurrence of certain thromboembolic phenomena has stimulated a search for inhibitors of platelet function. This report presents data to indicate that nitrofurantoin is a potent inhibitor of primary ADP-induced platelet aggregation. The addition of 10 muM nitrofurantoin to citrated platelet-rich plasma obtained from 12 normal subjects produced a 29+/-6% (2 SD) inhibition of the velocity of platelet aggregation induced by 2 muM ADP. The inhibitory effect of nitrofurantoin demonstrated competitive kinetics in respect to ADP. The intravenous (180 mg) or oral (200 mg) administration of nitrofurantoin produced a serum nitrofurantoin concentration ranging from 2.7 to 23 muM in 28 normal subjects. Platelet-rich plasma obtained from these subjects demonstrated inhibition of the velocity of ADP-induced platelet aggregation that correlated with the log of the serum nitrofurantoin concentration (P < 0.001). Collagen-induced platelet aggregation was also inhibited in a dose-related manner, and the bleeding time was significantly prolonged in the two subjects with the highest serum nitrofurantoin concentration. These studies indicate that nitrofurantoin in vivo inhibits platelet function to a degree that is proportional to the serum nitrofurantoin concentration.