Antibiotic Dosing in CKD Pregnancy: Avoid if possible — aminoglycosides cross placenta; irreversible 8th cranial nerve damage in fetus reported. Use only when life-threatening and no alternatives.

Gentamicin (Renal Dosing/TDM)

Brand names: Cidomycin

Adult dose

Dose: 5-7 mg/kg once daily (extended-interval dosing) for most indications. Endocarditis/synergy: 1 mg/kg every 8 hours. Loading dose: 5-7 mg/kg regardless of renal function.

Route: Intravenous infusion over 30 minutes

Frequency: Once daily (extended-interval); every 8 hours (synergy dosing)

Max: 7 mg/kg loading dose; subsequent doses per TDM

Aminoglycoside — concentration-dependent bactericidal activity. Extended-interval dosing achieves high peak concentrations (Cmax/MIC) exploiting concentration-dependent killing and post-antibiotic effect, while minimising trough (reducing nephrotoxicity). TDM after first dose in CKD.

Paediatric dose

Dose: 7 mg/kg

Route: IV infusion

Frequency: Once daily (adjust for renal function)

Max: Per TDM

Neonates: 4-5 mg/kg once daily (adjust for gestational age — BNFc neonatal section). TDM mandatory from the start. MHRA 2012: gentamicin once-daily dosing preferred in neonates to reduce nephrotoxicity.

Dose adjustments

Renal

Critical: extend dosing interval based on eGFR and TDM. Hartford nomogram or Bayesian methods used. Target pre-dose (trough) <1 mg/L (extended-interval) to prevent accumulation and nephrotoxicity. Avoid in severe CKD (eGFR <20) unless no alternatives — risk of irreversible nephrotoxicity and ototoxicity.

Hepatic

No dose adjustment required — not hepatically metabolised

Paediatric weight-based calculator

Patient weight (kg)

Clinical pearls

TDM protocol: extended-interval (OD) dosing — measure level 6-14 hours after FIRST dose; use Hartford nomogram or Bayesian calculator to determine next dose timing. Trough <1 mg/L before next dose confirms safe interval.
Vestibulotoxicity is the most clinically significant toxicity of gentamicin: patients develop oscillopsia (visual image bouncing with head movement) and disequilibrium. Risk is cumulative and often irreversible — monitor vestibular function in prolonged courses.
Intraperitoneal gentamicin for peritoneal dialysis (PD) peritonitis: 0.6 mg/kg/day added to dialysis fluid — TDM required. Local PD peritonitis protocols define exact dosing.
Gentamicin ear drops (Genticin): topical preparation for otitis externa — systemic absorption minimal; NOT for use with perforated tympanic membrane (ototoxicity risk).
Surgical prophylaxis: single 5 mg/kg IV dose before certain procedures (bowel surgery, biliary); no TDM required for single-dose use.

Contraindications

Myasthenia gravis (aminoglycosides block neuromuscular junction)
Hypersensitivity to gentamicin or aminoglycosides
Concurrent use with other ototoxic/nephrotoxic drugs (avoid unless essential)

Side effects

Nephrotoxicity (tubular injury — reversible if detected early; irreversible if prolonged)
Ototoxicity — vestibulotoxicity (disequilibrium, oscillopsia) and cochleotoxicity (hearing loss); often irreversible
Neuromuscular blockade (high doses in myasthenia)
Hypersensitivity (rare)

Interactions

Vancomycin — additive nephrotoxicity and ototoxicity; mandatory combined TDM
Loop diuretics (furosemide) — additive ototoxicity
NSAIDs — additive nephrotoxicity
Neuromuscular blocking agents — enhanced blockade (surgical setting)

Monitoring

Serum gentamicin levels (first trough at 18-24h after extended-interval dose)
Creatinine/eGFR (daily in high-risk patients)
Vestibular function (prolonged courses)
Hearing assessment (audiometry for prolonged use)

Reference: BNFc; BNF 90; BNFc; Hartford Nomogram; NICE NG15 (Antimicrobial Stewardship); PHE Guidelines; SPC Cidomycin. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

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