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Aminoglycoside Antibiotic Pregnancy: Avoid unless no safer alternative — risk of fetal ototoxicity and nephrotoxicity

Gentamicin

Brand names: Gentamicin (generic)

Adult dose

Dose: Once-daily (Hartford/Bode): 5–7 mg/kg IV once daily (target trough <1 mg/L). Conventional (BD/TDS): 1–2 mg/kg every 8h (target pre-dose <2 mg/L, peak 5–10 mg/L).
Route: IV infusion over 30 min
Frequency: OD (preferred in most cases) or TDS (neonatal and endocarditis protocols)
Max: 7 mg/kg single dose
Once-daily dosing preferred in adults — equal efficacy, less nephrotoxicity. Therapeutic drug monitoring essential. Synergistic with beta-lactams for endocarditis.

Paediatric dose

Dose: 7 mg/kg
Route: IV infusion over 30 min
Frequency: OD (>1 month); neonates: per gestational age protocol
Max: 7 mg/kg per dose
Concentration: 40 mg/ml
BNF for Children: children ≥1 month: 7 mg/kg OD IV. Neonates (gestational age-based): <35 weeks: 5 mg/kg every 36h; 35–37 weeks: 5 mg/kg every 36h; ≥37 weeks <7 days: 4 mg/kg every 24h. TDM essential — trough <1 mg/L before next dose. Source: BNF for Children 2024; Hartford Nomogram

Dose adjustments

Renal

Significantly reduced in renal impairment — extend interval and reduce dose per nomogram. Monitor trough levels assiduously.

Hepatic

No hepatic dose adjustment (renally excreted)

Paediatric weight-based calculator

BNF for Children: children ≥1 month: 7 mg/kg OD IV. Neonates (gestational age-based): <35 weeks: 5 mg/kg every 36h; 35–37 weeks: 5 mg/kg every 36h; ≥37 weeks <7 days: 4 mg/kg every 24h. TDM essential — trough <1 mg/L before next dose. Source: BNF for Children 2024; Hartford Nomogram

Clinical pearls

  • Pre-dose (trough) level: take 23–24h after dose (OD regimen); must be <1 mg/L before next dose
  • Ototoxicity: irreversible; counselling essential before prolonged courses; baseline audiometry for chronic use
  • Endocarditis: low-dose gentamicin synergy (1 mg/kg every 8h, targeting trough <1 mg/L) — check renal function daily; stop if creatinine rises >50 micromol/L
  • Pabrinex contains no gentamicin — do not confuse with other IV solutions

Contraindications

  • Myasthenia gravis (neuromuscular blockade risk)
  • Concurrent nephrotoxic/ototoxic drugs where avoidable

Side effects

  • Nephrotoxicity (trough-level dependent)
  • Ototoxicity (vestibular and cochlear — irreversible, cumulative)
  • Neuromuscular blockade (rare, at high doses)
  • Rash

Interactions

  • Loop diuretics (furosemide) — additive ototoxicity
  • NSAIDs — increased nephrotoxicity
  • Neuromuscular blocking agents — enhanced blockade
  • Cisplatin — additive nephrotoxicity and ototoxicity

Monitoring

  • Trough levels (pre-dose) at steady state
  • Renal function (daily in high-risk patients)
  • Signs of ototoxicity (hearing loss, tinnitus, vertigo)
  • Fluid balance

Reference: BNFc; BNF; BNF for Children; BSAC Endocarditis Guidelines; Hartford Nomogram. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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