Inhibition of platelet aggregation by moxalactam and free N-methylthiotetrazole.

The effects of moxalactam and free N-methylthiotetrazole (N-MTT) in vitro on platelet aggregation induced by adenosine diphosphate (ADP), arachidonic acid, collagen, epinephrine, or ristocetin were determined. Moxalactam at concentrations of 1.9 mM and 5.7 mM inhibited platelet aggregation induced by ADP, arachidonic acid, epinephrine, and ristocetin. Although the aggregatory activity of collagen was not inhibited with 1.9 mM moxalactam, an increase in the concentration of moxalactam to 5.7 mM significantly inhibited collagen-induced platelet aggregation. Inhibition of platelet aggregation by free N-MTT was also concentration dependent. The lowest concentration of N-MTT used in this study, 5.7 mM, inhibited platelet aggregation induced by both arachidonic acid and ristocetin. At a concentration of 28 mM, N-MTT inhibited aggregation induced by ADP, collagen, epinephrine, and ristocetin, but not by arachidonic acid. At 57 mM N-MTT, almost complete inhibition of platelet aggregation occurred for all five agonists tested.