Severe tachycardia following low-dose clozapine treatment

Abstract

Objective: To reporta case of severe and sustained tachycardia that developed asymptomatically on a low dose of clozapine (ISO mg daily).Method:Case report.Results:Serially monitored 24 h heart rate after the introduction of clozapine showed an increase in the 24 h mean from 87 to 126 bpm, a reduction of pulse variability and anomalies in sleep-wake regulation. Cessation of clozapine was followed by a rapid return to preclozapine activity. Application of the Naranjo Adverse Drug Reaction Probability Scale indicated a probable relationship between clozapine and the sustained tachycardia.Conclusions: Severe and sustained tachycardia can develop asymptomatically with a relatively low dose of clozapine and a slow titration rate. The severity of the tachycardia may not be revealed in isolated pulse measurements and may escape clinical detection without closer monitoring of heart rate.