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Aminoglycoside Antibiotic Pregnancy: Avoid — cochlear and vestibular damage in fetus; use only if life-threatening and no alternative

Gentamicin (Orthopaedic — Bone Cement and Systemic)

Brand names: Cidomycin, Garamycin, Simplex with Tobramycin (cement)

Adult dose

Dose: Systemic: 5–7 mg/kg IV once daily (Hartford nomogram); Bone cement: gentamicin-impregnated PMMA cement (0.5–4 g per 40 g packet)
Route: Intravenous (systemic); local (cement)
Frequency: Once daily (systemic — Hartford protocol)
Max: 7 mg/kg/day (systemic); guided by Hartford nomogram and drug levels
Once-daily dosing (Hartford nomogram) is now standard — reduces toxicity vs traditional divided-dose regimens. Check levels: pre-dose level <1 mg/L and 6–14 hour level plotted on Hartford nomogram. Gentamicin bone cement: locally impregnated PMMA provides high local concentration with minimal systemic levels.

Paediatric dose

Dose: 5–7 mg/kg
Route: Intravenous
Frequency: Every 24 hours
Max: Use Hartford nomogram for age-appropriate dosing
Paediatric osteomyelitis — age and weight-based dosing; monitor levels closely; paediatric nomogram differs from adult

Dose adjustments

Renal

Extended dosing intervals in renal impairment — accumulation causes ototoxicity (irreversible) and nephrotoxicity; consult microbiology or pharmacist; avoid if eGFR <30 mL/min unless no alternative

Hepatic

No dose adjustment — renally eliminated

Paediatric weight-based calculator

Paediatric osteomyelitis — age and weight-based dosing; monitor levels closely; paediatric nomogram differs from adult

Clinical pearls

  • Hartford nomogram (once-daily gentamicin): 5–7 mg/kg IV loading dose regardless of renal function, then plot 6–14 hour level on nomogram to determine dosing interval (24h, 36h, or 48h) — validated for Gram-negative infections, not endocarditis
  • Vestibulotoxicity is IRREVERSIBLE: unlike nephrotoxicity which is usually reversible, vestibular damage from aminoglycosides is permanent — balance assessment and audiometry monitoring in prolonged courses; cumulative lifetime exposure matters
  • Gentamicin bone cement: standard in UK arthroplasty practice — PMMA cement releases gentamicin at high local concentration (>1000 mg/L joint fluid) for months; systemic levels from cement are negligible; synergy with systemic antibiotics for post-surgical infection prevention
  • Prophylaxis at arthroplasty: gentamicin 1.5 mg/kg IV (single pre-operative dose) is used as an alternative to cefuroxime for penicillin-allergic patients; local guidelines vary
  • MHRA: combination of gentamicin + furosemide is a recognised cause of profound ototoxicity — avoid concurrent administration; if unavoidable, separate doses and monitor hearing

Contraindications

  • Known hypersensitivity to aminoglycosides
  • Severe renal impairment without therapeutic monitoring
  • Myasthenia gravis (neuromuscular blockade worsening)

Side effects

  • Vestibulotoxicity — IRREVERSIBLE; imbalance, ataxia, oscillopsia; cochlear damage less common than with streptomycin but occurs
  • Nephrotoxicity — acute tubular necrosis; reversible if caught early; accumulation risk in CKD
  • Neuromuscular blockade at high doses
  • Ototoxicity — high-frequency hearing loss

Interactions

  • Vancomycin — additive nephrotoxicity; monitor renal function closely
  • Loop diuretics (furosemide) — additive ototoxicity; MHRA warning
  • Neuromuscular blocking agents — enhanced blockade

Monitoring

  • Gentamicin levels: pre-dose (<1 mg/L) and 6–14 hour post-dose (Hartford nomogram)
  • Renal function daily
  • Signs of vestibular toxicity — dizziness, ataxia
  • Audiometry if prolonged use

Reference: BNFc; BNF 90; Hartford Nomogram (Aminoglycoside Dosing); NICE NG15; MHRA Ototoxicity Warning; NICE NG124; SPC Cidomycin. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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