Persistent Tachycardia in a Patient on Clozapine

Tachycardia emergent from clozapine treatment is usually transient, often missed, unreported, and therefore frequently goesuntreated resulting in possible premature discontinuation of an otherwise effective treatment. Clozapine-induced tachycardiaresults from direct effects on the sympathetic nervous system including the blockade of cardiac muscarinic M2receptors,presynapticα2adrenoceptors, and indirect activation of theβadrenoceptors. Unfortunately, there are no clear guidelines formonitoring or treating tachycardia induced by clozapine. We present a case of a 55-year-old man with treatment-resistantschizophrenia initiated on clozapine who developed persistent tachycardia and right bundle branch block in the course oftreatment. Tachycardia persisted despite treatment with metoprolol and necessitated a transfer to the intensive care unit. Areduction in clozapine dose with the addition of adjunctive antipsychotic(lurasidone) stabilized the patient’s heart rate. This casehighlights the need for consistent physical examination and a multidisciplinary-based treatment approach for patients onclozapine. The case also suggests that clozapine dose reduction and combination antipsychotic treatments may preclude theneed to discontinue clozapine in patients with persistent tachycardia.