PLATELET 5-HYDROXYTRYPTAMINE IS DECREASED IN A PRELIMINARY GROUP OF DEPRESSED-PATIENTS RECEIVING THE 5-HYDROXYTRYPTAMINE REUPTAKE INHIBITING DRUG FLUOXETINE

1. In view of the importance of 5-hydroxytryptamine in coronary thromb osis, we wanted to know whether a potentially protective decrease in p latelet 5-hydroxytryptamine could be achieved by treatment with an inh ibitor of 5-hydroxytryptamine uptake, fluoxetine. 2. We studied 15 pat ients treated for psychiatric indications with fluoxetine, and compare d the findings with those obtained with blood from 18 patients treated with amitriptyline and 13 controls previously treated for affective d isorders. 3. Platelet-rich plasma 5-hydroxytryptamine levels were sign ificantly decreased in the fluoxetine group (P<0.005) but not in the a mitriptyline group compared with the control group. 4. Collagen-induce d aggregation in whole blood anticoagulated with hirudin was measured by sequential single platelet counting. The contribution of 5-hydroxyt ryptamine was assessed from the effect of adding the 5-hydroxytryptami ne specific antagonist ICI 170809. This contribution was significantly decreased in the fluoxetine group but not in the amitriptyline group compared with the control group. 5. It is concluded that platelet 5-hy droxytryptamine is indeed decreased by fluoxetine, and we would predic t a protective effect of fluoxetine against coronary thrombosis.