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 μM 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 μM 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 μM 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.