Lack of antiplatelet activity of the new coumarin derivative 8-monochloro-3-beta-diethylaminoethyl-4-methyl-7-ethoxy- carboxylmethoxycoumarin under in vivo conditions in man.

Antiplatelet properties of AD 6 (8-monochloro-3-beta-diethylaminoethyl-4-methyl-7-ethoxy-carboxyl- methoxycoumarin) have been studied in vitro and in vivo. The drug showed a marked inhibitory effect on platelet aggregation, beta-thromboglobulin (beta TG) release and thromboxane B2 (TxB2) production in vitro. However, such effects were seen only in the presence of high concentrations of the drug (10(-3) and 10(-4) mol/l) and completely disappeared at lower concentrations. No effect was seen in vivo following oral administration of 300 mg of the drug in a small group of volunteers. It can be concluded that in vitro properties of the drug cannot be surmised without due caution to indicate its potential clinical use.