Diphenhydramine-Induced Torsade De Pointes With Pharmacological Cardioversion in a Patient With Methadone-Induced QT Prolongation.

The anesthetic management of patients with chronic pain requires a thorough understanding of the physiologic changes resulting from long-term exposure to opioids, as well as a firm comprehension of the pharmacodynamic and pharmacokinetic properties of these medications. We present the case of a 60-year-old woman on methadone therapy presenting for cervical laminectomy and fusion. After intraoperative dysrhythmias, she underwent pharmacological cardioversion from torsade de pointes. This occurred intraoperatively after receiving 25 mg of intravenous diphenhydramine to attenuate erythema thought to be secondary to antibiotic administration. The use of a routine antihistamine may present a torsadogenic reaction in the setting of methadone maintenance treatment.