Spironolactone and trimethoprim — GPhC CRA MCQ

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HardDrug InteractionsSpironolactone and trimethoprimGPhC CRA

A patient taking sertraline 100 mg daily is prescribed linezolid for a resistant infection. The infection team has not documented a plan for the antidepressant or toxicity monitoring. What is the safest pharmacy action?

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Correct answer: D — Pause dispensing and agree a specialist interaction-management plan

Pause dispensing and agree a specialist interaction-management plan: Linezolid is a reversible monoamine-oxidase inhibitor and can precipitate serotonin syndrome with serotonergic antidepressants; urgency of infection, alternatives, supervised interruption and monitoring must be agreed rather than improvised. Supply both medicines and monitor blood pressure during treatment: Serotonin syndrome, including neuromuscular and autonomic toxicity, is the central interaction concern and blood pressure alone is insufficient. Supply linezolid after omission of one sertraline dose: One omitted dose does not reliably remove serotonergic exposure, and interruption requires a documented multidisciplinary plan. Replace sertraline with fluoxetine on the first linezolid day: Fluoxetine is also serotonergic and has a long half-life, so same-day substitution compounds rather than resolves the interaction. Continue both medicines with doses separated by twelve hours: A pharmacodynamic monoamine-oxidase interaction is not prevented by spacing administration times.

Reference: BNF: linezolid: https://bnf.nice.org.uk/drugs/linezolid/; BNF: sertraline: https://bnf.nice.org.uk/drugs/sertraline/