Before starting methadone maintenance therapy, which baseline investigation is specifically recommended because of a class-related adverse effect of the drug?

• A Electrocardiogram to measure the QT interval ✓
• B Serum amylase to screen for pancreatic injury
• C Nerve conduction study to detect peripheral neuropathy
• D Audiometry to detect ototoxicity

Explanation

Methadone prolongs the QT interval in a dose-dependent manner by blocking cardiac potassium channels, and it has caused torsades de pointes and sudden death, particularly at higher maintenance doses. A baseline ECG with follow-up after dose titration is recommended. Methadone is not associated with clinically significant pancreatic, neural, or auditory toxicity that would justify the other tests.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.