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Lithium and ACE inhibitor — GPhC CRA MCQ

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HardDrug InteractionsLithium and ACE inhibitorGPhC CRA

A 63-year-old man stabilised on lithium for bipolar disorder is newly prescribed lisinopril for hypertension. Baseline eGFR is 55mL/min/1.73m2 and sodium is 134mmol/L. He had lithium toxicity during dehydration last year. What is the most important interaction to flag?

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Correct answer: E — Lisinopril may increase lithium concentration and toxicity risk

ACE inhibitors can increase lithium concentrations and toxicity risk, especially with renal impairment or sodium depletion. The patient's eGFR, low-normal sodium and previous toxicity increase concern. The prescriber should plan lithium and renal monitoring or consider alternatives. Blood pressure effect is not the key safety issue.

Reference: BNF Lithium interactions; NICE CKS Bipolar disorder