Co‐administration of sertraline and haloperidol

Along with recent increased interest in the selective serotonin reuptake inhibitors, a number of studies has been undertaken to observe interactions with different drugs. When selective serotonin reuptake inhibitor was administered together with antipsychotics to schizophrenics showing depressive or obsessive symptoms and negative symptoms, meaningful results were observed. The objective of our research was to identify the changes in the concentration of plasma haloperidol when sertraline was administered to patients who already were being treated with haloperidol. Sixteen patients who did not respond to the traditional antipsychotics after 2 weeks of treatment with a certain dosage of haloperidol were administered with 50 mg of sertraline for a period of 2 weeks. The concentration changes between plasma haloperidol and the reduced haloperidol were observed using high‐powered liquid chromatography equipped with a UV detector. There was a significant increase (P< 0.01) in the concentration of haloperidol, the change being from 8.52 ± 4.22 to 10.91 ± 5.38 ng/mL. However, the change in the concentration of reduced haloperidol was from 7.41 ± 7.93 to 5.22 ± 6.10 ng/mL, showing a significant decrease. The concentrations of total plasma haloperidol showed no significant changes at all. In comparing the ratio of the reduced haloperidol and the haloperidol, the reduction ratio was down to 0.39 ± 0.27 from 0.94 ± 0.65 showing a significant decrease. There seems to be few studies done on interactions using serotonergic drugs together with antipsychotics in spite of their clinically applicable possibility. According to similar studies done in the past, co‐administering of such drugs not only increases the plasma concentration of antipsychotics, but it also results in clinical improvement of negative symptoms and aggravation of extrapyramidal symptoms. Changes in clinical symptoms and adverse effects were not observed in our study. However, we think these observations need to be included in upcoming larger scale studies.