Effect of oral contraceptives on platelet noradrenaline and5-hydroxytryptamine receptors and aggregation.

Characteristics of receptor sites on platelets for noradrenaline (NA) and serotonin (5-HT) changed significantly between day 21 and day 28 of treatment in healthy women taking oral contraceptives. NA-induced and 5-HT-induced platelet aggregation and 5-HT uptake vaired accordingly. In untreated women with normal cycles no changes in either receptor site or in platelet function occurred between the luteal and postmenstrual phases. It is concluded that the observed changes are due to a pharmacological effect of the oral contraceptive rather than a normal physiological variation.