The study's primary comparison was between thioridazine, which has a marked effect on the electrocardiogram, and haloperidol, which has less of an effect. "Overall, the risk with thioridazine was no worse than that with haloperidol. Thioridazine may, however, represent an elevated risk at high doses," said Sean Hennessy, PharmD, PhD, assistant professor in Penn's Department of Biostatistics and Epidemiology. "To reduce cardiac risk, thioridazine should be prescribed at the lowest dose needed to obtain an optimal therapeutic effect."
Hennessy and his colleagues conducted a cohort study of billing data collected between 1993 and 1996 from three Medicaid programs. The researchers included patients with more than one prescription for oral thioridazine and haloperidol, as well as the antipsychotic drugs risperidone and clozapine, plus at least two instances of a schizophrenia diagnosis. They compared the records of these patients with two control groups - one group of glaucoma patients and one group of psoriasis patients - since both patient types require periodic prescriptions and are not associated with cardiovascular problems. In all, they looked at data taken from over 120,000 patients.
"We compared the frequency of cardiac arrest and ventricular arrhythmia associated with different antipsychotic drugs versus the control groups," said Hennessy. "Our findings clearly link patients with treated schizophrenia to high
Contact: Greg Lester
University of Pennsylvania School of Medicine