The action of antidepressant drugs on 5-hydroxy-tryptamine uptake by platelets--relationship to therapeutic effect.

The uptake of 5-hydroxytryptamine (5-HT) by the blood platelets of depressive patients treated with amitriptyline and zimelidine has been examined. Both drugs significantly reduce the uptake of 5-HT into the platelet and the degree of inhibition is correlated with the plasma drug level of amitriptyline. No significant correlations could be detected between the degree of inhibition of uptake and clinical change. The accepted mode of action of tricyclic antidepressant drugs, i.e. the inhibition of reuptake of released amines, is discussed.