QTc and psychopharmacs: are there any differences between monotherapy and polytherapy

BACKGROUND Some psychotropic drugs are connected with prolongation of QT interval, increased risk of cardiac arrhythmias and greater incidence of sudden death, especially when used in combination. Concomitant use of antipsychotics and antidepressants is not rare in our clinical practice. The study compares the length of QT interval in patients on monotherapy with an antipsychotic or an antidepressant and patients taking polytherapy (an antipsychotic agent combined with an antidepressant). METHODS Sixty-one hospitalized women who met the ICD-10 criteria for schizophrenia, schizoaffective psychosis, delusional disorder and mood disorder were included in the study. The monotherapy group was consisted of thirty-two women treated with an antipsychotic or an antidepressant while the polytherapy group was composed of twenty-nine women treated with an antipsychotic agent plus an antidepressant. Two electrocardiograms (ECGs) were obtained for each patient: the first was carried out before the treatment and the second after two weeks of treatment.Statistical analysis was carried out by SPSS program and included unpaired and paired t test and Fisher's exact test. RESULTS Mean baseline QTc values did not differ between the groups (439 +/- 22 ms was the same value found in the both groups; unpaired t test, p > 0.5). Mean QTc intervals after two weeks of treatment were also similar (439 +/- 24 ms in the monotherapy group and 440 +/- 20 ms in the polytherapy group; unpaired t test, p > 0.5). Fisher's exact test did not reveal significant difference in the number of patients with borderline (451-470 ms) or prolonged (> 470 ms) QTc between groups, neither before treatment nor after two weeks of treatment. Twenty two women of the total of sixty one patients (36%) had QTc > 450 ms before applying therapy. CONCLUSION We did not find significant QT prolongation in our patients after two weeks of treatment with antipsychotics and/or antidepressants. The QTc interval length did not differ significantly in the monotherapy and the polytherapy group. More than one third of included women exceeded the threshold value of borderline QTc interval (450 ms) before starting treatment. This finding calls for caution when prescribing drugs to female psychiatric patients, especially if they have other health problems.