Objective: To assess the cardiovascular safety of two commonly prescribed atypical antipsychotics risperidone (RSP) and olanzapine (OZP) in schizophrenic patients, using electrocardiography (ECG) and Blood Pressure (BP).
Materials and methods: This was a 10-week prospective open label, observational study, carried out in a newly diagnosed 64 schizophrenic patients receiving either RSP or OZP. RSP (n = 32) was started with dose of 2 mg/day and increased to 4 mg/day after 2 weeks, whereas OZP (n = 32) was started at a dose of 5 mg/day and was increased to 10 mg/day after 2 weeks. Heart rate (HR), ECG parameters (PR, RR, QRS, QT intervals and QTc and QTd) and BP (systolic and diastolic in supine and standing position) were recorded at baseline (before drug therapy)) and during follow-up visits at 2(I), 6(II) and 10(III) weeks.
Results: In the RSP group, at II and III follow-ups, a significant increase in the HR (P = 0.018, P = 0.011 respectively) as well as in QTc (P = 0.025, P = 0.015, respectively) was observed when compared to the basal values. In the OZP group, diastolic BP was significantly decreased in standing position at II and III follow-ups (P = 0.045 and P = 0.024, respectively) compared to the basal values. When the two groups were compared with each other, no significant differences were observed in the changes of HR, PR, QRS, QT, RR, QT, QTd and SBP (supine and standing position); and DBP (supine position). However, DBP in standing position showed a significant decrease in the OZP group at II and III follow-up (P = 0.036 and P = 0.016, respectively) compared to the RSP group.
Conclusions: Patients treated with OZP are at higher risk to develop postural hypotension as compared with RSP; hence RSP could be better tolerated by patients taking antihypertensive drugs as compared with OZP whereas OZP would have a safer cardiac profile.
Keywords: ECG changes; QTc; QTd; heart rate; olanzapine; risperidone.