Chronic treatment with clomipramine or maprotiline depletes platelet serotonin and modifies its diurnal rhythm

Abstract

1. 1. Endogenous depressive patients were treated either with clomipramine (a predominantly 5HT uptake inhibitor) or maprotiline (a selective NA uptake inhibitor). 2. 2. Platelet 5HT rapidly decreased after clomipramine to a minimum (20% pretreatment values) within two weeks, and an abnormal 5HT diurnal rhythm tended towards the control pattern or was abolished. 3. 3. Unexpectedly, after maprotiline a transient increase in 5HT was followed by a decrease; the abnormal 5HT diurnal rhythm was exaggerated. The effect of maprotiline on platelet 5HT was probably secondary. 4. 4. Platelet 5HT measurements may be useful as an indirect estimation of clomipramine plasma level and efficacy of uptake inhibition; the therapeutic effect may however be less related to this presynaptic event than long-term post-synaptic changes in receptor sensitivity modifying abnormal 5HT rhythms.