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Profound metoprolol‐induced bradycardia precipitated by acetaminophen‐propoxyphene
Author(s) -
Marraffa Jeanna M.,
Lang Li,
Ong Gilbert,
Lehmann David F.
Publication year - 2006
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1016/j.clpt.2005.11.014
Subject(s) - propoxyphene , metoprolol , medicine , bradycardia , acetaminophen , cyp2d6 , anesthesia , analgesic , ingestion , pharmacology , metoprolol tartrate , heart rate , cytochrome p450 , blood pressure , metabolism
Pharmacokinetic studies demonstrate that propoxyphene is a potent inhibitor of cytochrome P450 (CYP) 2D6. Clinically significant sequelae have not been previously reported. We report a case of this inhibition manifested by life‐threatening bradycardia in a patient receiving a CYP2D6 substrate, metoprolol. A 48‐year‐old man came to the emergency department complaining of dizziness 3 hours after ingesting metoprolol, at his usual dose, and 2 tablets of propoxyphene, newly begun postoperatively. Four hours after ingestion of both drugs, the patient was noted to have a ventricular rate of about 30 beats/min with underlying atrial fibrillation. The patient's ventricular response returned to normal within 11 hours of ingestion. We have demonstrated the clinical importance of the interaction between propoxyphene and metoprolol likely resulting from inhibition of hepatic clearance of metoprolol by propoxyphene. Underscoring the clinical relevance of CYP2D6 inhibition by an analgesic of questionable efficacy should proscribe its use. Clinical Pharmacology & Therapeutics (2006) 79 , 282–286; doi: 10.1016/j.clpt.2005.11.014