Several antipsychotic medications used to treat schizophrenia may increase a patient's risk for cardiac arrest and ventricular arrhythmia, says a new report published in the November 9th issue of the British Medical Journal. Using data collected between 1993 and 1996 by officials with the U.S. Medicaid program, scientists from the University of Pennsylvania School of Medicine in Philadelphia studied the effects of clozapine, risperidone and thioridazine on thousands of patients. The rate ratios for heart problems among patients treated with the medications ranged from 1.7 to 3.2.

In the past, antipsychotic drugs have also been linked to two serious complications known as Neuroleptic Malignant Syndrome (NMS) and Tardive Dyskinesia. NMS is a potentially fatal syndrome involving muscle rigidity, an altered mental status and symptoms of cardiac instability (irregular blood pressure, tachycardia, irregular pulse). Tardive Dyskinesia is a central nervous system disorder characterized by involuntary movements of the limbs as well as twitching of the face and tongue.