Theophylline toxicity from macrolide inhibition — MRCPCH TAS MCQ

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HardPharmacologyTheophylline toxicity from macrolide inhibitionMRCPCH TAS

A 13-year-old taking modified-release theophylline develops vomiting, palpitations and seizures after treatment for atypical pneumonia. Theophylline concentration is high. Which co-prescribed drug is most likely responsible?

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Correct answer: E — Erythromycin

Erythromycin can inhibit hepatic metabolism of theophylline, increasing concentrations and toxicity risk. Amoxicillin does not usually raise theophylline levels. The pearl is that theophylline has a narrow therapeutic index and many clinically relevant drug interactions.

Reference: BNFc; Nelson Textbook of Pediatrics; RCPCH Theory examination syllabi