The pharmacokinetics and pharmacologic effects of a potent, selective inhibitor of thromboxane synthetase, CV-4151 [(E)-7-phenyl-7-(3-pyridyl)-6-heptenoic acid] on prostanoid formation and platelet aggregation were studied in 42 healthy male volunteers. The drug was well tolerated. After oral administration of 10 to 100 mg of CV-4151, peak plasma levels of 1-6 9g/mL were reached in a dose-dependent manner within 1 hour. Elimination followed first-order fashion with elimination half-life of about 1 hour. Serum levels of thromboxane B 2 reduced to 4% to 15% of control at 2 hours after drug ingestion dose-dependently. Serum levels of 6-keto-prostaglandin Fla increased to about four to six times basal levels. Platelet aggregation induced by collagen and arachidonate was inhibited in most cases. Such pharmacologic effects outlasted serum drug levels. In repeated administration, stable inhibition of serum thromboxane B 2 production and platelet aggregation in proportion to the enhancement of serum 6-keto-prostaglandin Fla production was observed although no drug accumulation was found. These results indicate that CV-415! may be suitable for clinical trials in cardiovascular diseases in which imbalance between thromboxane and prostacyclin may be involved in the pathogenesis.