Aminoglycoside toxicity risk in septic shock — FFICM MCQ

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ModeratePharmacologyAminoglycoside toxicity risk in septic shockFFICM

A 71-year-old woman with septic shock received gentamicin in the emergency department. She has AKI with eGFR 18 ml/min/1.73 m2 and is now clinically improving on piperacillin-tazobactam. A gentamicin level taken 18 hours after dosing is still above the redosing threshold. What is the most appropriate management?

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Correct answer: B — Withhold further gentamicin and recheck levels

The correct answer is B, withhold further gentamicin and recheck levels. In AKI (eGFR 18 ml/min/1.73 m2), gentamicin clearance is markedly reduced, so a trough level taken at 18 hours that remains above the redosing threshold indicates the drug has not yet cleared enough for a further dose to be given safely. UK once-daily aminoglycoside protocols mandate checking a trough (pre-dose) level before any repeat dose; if it remains elevated, the next dose is withheld and the level rechecked at intervals until it falls below threshold, at which point dosing can resume or be adjusted. Piperacillin-tazobactam is already covering the gram-negative sepsis adequately, so there is no clinical urgency that justifies risking further nephrotoxic or ototoxic accumulation. This approach protects residual renal function while still allowing gentamicin to be restarted safely once levels confirm adequate clearance.

Reference: Kent and Medway NHS Formulary, Gentamicin Once Daily Dosing and Monitoring Protocol: trough level must be checked 18 to 24 hours after the first dose before any redosing decision is made, https://www.kentandmedwayformulary.nhs.uk/media/pjacwphy/gentamicin-once-daily.pdf