The object of this study was to investigate a possible pharmacological effect of fluoxetine on haemostatic function, with special attention on primary haemostasis, in order to explain haemorrhagic complications reported in some treated, depressed patients. The haemostatic function of depressive patients, who required fluoxetine therapy, was studied before and after 1 month of treatment with fluoxetine 20 or 40 mg daily. Exclusion criteria were: pregnancy, initial abnormal haemostatic function, history of coagulation abnormalities, treatment with drugs that interfere with haemostasis, and recent fluoxetine therapy. The following tests were performed: prothrombin time, partial thromboplastin time, thrombin time, plasma fibrinogen, platelet counts, bleeding time, platelet aggregation induced by ADP, epinephrine, ristocetin, collagen, arachidonic acid, and plasma determination of fluoxetine and norfluoxetine levels. Statistical analysis was performed by Wilcoxon paired sample, one-tailed test (alpha=0.05). Among 18 patients included, only eight completed the trial. The single statistically significant difference was a decreased velocity in platelet aggregation induced by epinephrine without increased bleeding time. The results failed to demonstrate any compromised haemostatic function after 20 mg daily fluoxetine therapy in patients with initial haemostatic function. However, the results suggest possible effects of fluoxetine on platelet adrenoreceptors.
Copyright 1998 John Wiley & Sons, Ltd.