Review of Gentamicin after 48-72 Hours

CAUTION: This guideline section does NOT apply to synergistic gentamicin for infective endocarditis.

Gentamicin at treatment dose requires mandatory review at 72 hours due to its narrow therapeutic index and risk of toxicity.

The 72-Hour Rule: Gentamicin must have been reviewed by 72 hours after the start of treatment with the intent to stop or switch. Cumulative doses beyond 3–5 days significantly increase the risk of irreversible ototoxicity.

Gram-Negative Continuity: For intra-abdominal and urinary tract infections (UTI), effective gram-negative cover must be maintained. Gentamicin must not simply be stopped; it requires a replacement agent that continues to provide appropriate gram-negative coverage based preferably on culture results or the NHS A&A rationalisation pathways in their absence.

Action at 72 hours:

  • Bone & Joint Infections: Ongoing gram-negative cover is usually not required, stop gentamicin without replacement unless culture results suggest gram-negative infection.
  • Moderate-severe Hospital-acquired Pneumonia (HAP): gentamicin acts as an “insurance policy" for gram-negative bacteraemia from a source other than HAP, which is more likely to be resistant to trimethoprim/co-trimoxazole. Stop gentamicin after 72 hours.
  • Upper or Complicated UTI: Review culture results and use agents reported as “S” or “I” to replace gentamicin. If no positive cultures are available, use table below for empirical replacements.
  • Intra-abdominal Infections: Review culture results and use agents reported as “S” or “I” to replace gentamicin. If no positive cultures are available, use table below for empirical replacements.

Table 1: Suggested empirical replacement to gentamicin after 72 hours therapy

Microbiological / treatment history Suggested gentamicin replacement

No recent antimicrobials (last 90 days)

AND

No history of trimethoprim resistance

AND

No history of ESBL-producing organisms

 Co-trimoxazole 960mg 12 hourly (PO if absorbing)

Recent antimicrobials (last 90 days)

AND 

No ESBL-producing organisms or piperacillin-tazobactam / ciprofloxacin resistance

Piperacillin-tazobactam IV 4.5g 8 hourly (replaces all 3 agents in surgical "triple therapy", and both amoxicillin and gentamicin for urosepsis)

If true penicillin allergy: Ciprofloxacin* PO 500mg 12-hourly
Only use IV if oral route compromised.
History of ESBL-producing organisms Base gentamicin replacement on reported susceptibilities for ESBL-producing isolate

*Fluoroquinolones are subject to a warning from the MHRA.

 

Guideline reviewed March 2026
Page updated July 2026



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