Severe tachycardia following low-dose clozapine treatment.
OBJECTIVE
To report a case of severe and sustained tachycardia that developed asymptomatically on a low dose of clozapine (150 mg daily).


METHODS
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.
Stampfer
Hans
H
University Department of Psychiatry and Behavioural Science, QEII Medical Centre, Nedlands, WA, Australia. hgstamp@cyllene.uwa.edu.au
Swanepoel
Peter
P
D014150:Antipsychotic Agents / Q000009:adverse effects* / Q000627:therapeutic use; D003024:Clozapine / Q000009:adverse effects* / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography; D006801:Humans; D011618:Psychotic Disorders / Q000175:diagnosis / Q000188:drug therapy*; D012720:Severity of Illness Index; D020178:Sleep Disorders, Circadian Rhythm / Q000139:chemically induced; D013610:Tachycardia / Q000139:chemically induced* / Q000175:diagnosis / Q000503:physiopathology
D014150:Antipsychotic Agents; D003024:Clozapine