Severe sinus bradycardia after initiation of bupropion therapy: a probable drug-drug interaction with metoprolol.

Bupropion is an increasingly prescribed agent to aid in smoking cessation. However it has important drug-drug interactions related to the cytochrome P450 system. One of these is its inhibition of the metabolism of the commonly used beta-blocker, metoprolol. The authors describe a case of severe bradycardia related to the addition of bupropion to the medical regimen of a patient on metoprolol.