The effects of nimodipine on platelet aggregation and arachidonic acid（AA）metabolism were studied in order to explore its effect on patients with thrombosis or cardiovas- cular disease.The results indicate that nimodipine（50-350μmol/L）significantly inhibits platelet aggregation induced by ADP

AA

and ionophore A23187 in a dose dependent manner.The inhibitory effects induced by ionophore A23187 could be partially antagonized by calcium（1 mmol/L）.When the substrate was AA and the enzyme was supplied by pig lung microsomes

nimodipine（50-400μmol/L）significantly reduced the generation of TXB

2

and 6-keto-PGF

1a

in parallel.When the substrate was prostaglandin endoperoxide

however

the levels of TXB

2

and 6-keto-PGF

1a

were not significantly altered in the same concentration range.The results suggest that nimodipine is a cyclooxygenase inhibitor

and its ability to inhibit platelet aggregation is related to its calcium blocking effect.