INCREASED PLATELET AGGREGATION IN PATIENTS RECEIVING CHLORPROMAZINE: RESPONSES TO 5‐HYDROXYTRYPTAMINE, DOPAMINE AND N‐DIMETHYL DOPAMINE

1 Platelet aggregation responses to 5‐HT, dopamine, N‐dimethyl dopamine and adenosine diphosphate were compared in normal subjects and patients treated with chlorpromazine (CPZ) for longer than 6 months. 2 We confirmed our previous finding that 5‐HT induced aggregation is enhanced in CPZ treated patients. 3 Increased aggregation responses were also observed with dopamine and N‐dimethyl dopamine. 4 Quantitative comparisons of aggregation rates and total changes in optical density of platelet rich plasma relative to adenosine diphosphate showed significant increases with 5‐HT, dopamine and N‐dimethyl dopamine. 5 Implication of dopaminergic mechanisms in the central effects of phenothiazines suggests that changes in dopamine induced aggregation responses may be useful in attempting correlations of clinical and pharmacological effects.