Effects of serotonin reuptake inhibitors on hemostasis

OBJECTIVE: To examine the hematologic safety profile of the selective serotonin reuptake inhibitors (SSRIs), with particular emphasis on the effects of these drugs on platelet aggregation. METHODS: Platelet aggregation studies were undertaken at baseline, and repeated 2 and 4 weeks after the initiation of treatment with an SSRI. Other investigations undertaken included analysis of serum electrolyte and liver enzyme concentrations, complete blood count, and coagulation studies. Patients were also assessed for clinical signs of bleeding. Eight patients (7 treated with fluoxetine, 1 with paroxetine) completed the study protocol. RESULTS: Repeated ANOVA revealed no abnormalities in platelet aggregation, hematopoiesis, or coagulation profile. No patient developed clinical signs of abnormal hemostasis during the study period. A statistically significant elevation in the mean serum bilirubin concentration was detected, but this was not of clinical significance. CONCLUSIONS: Although the SSRIs may cause abnormal hemostasis, this effect is probably rare. Another possibility is that abnormal hemostasis is more likely to occur when high doses of SSRIs are administered.