Aminoglycoside Antibiotic Pregnancy: No proven cases of intrauterine damage; use in pregnancy only in life-threatening situations where expected benefits outweigh possible risks. In the absence of gastro-intestinal inflammation, amount ingested from milk is unlikely to result in significant blood levels in breast-fed infants.

Gentamicin

Brand names: Gentamicin (generic)

Used in: Acute Appendicitis

Gentamicin is a parenteral aminoglycoside antibiotic used for serious Gram-negative sepsis, including biliary, urinary and intra-abdominal infection, and in synergistic combinations for endocarditis.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 3–5 mg/kg/day (based on ideal body weight)

Route: intravenous or intramuscular

Frequency: once daily (preferred) or in two divided doses

Infectious diseases variant. Adults with normal renal function: 3–5 mg/kg/day depending on severity of infection, as one single dose (preferred) or two divided doses; adjust to clinical response and serum concentration; dose calculations based on ideal body weight. Urinary tract infection (normal renal function): 160 mg once daily may be used. Once-daily dosing is not recommended in endocarditis. Therapeutic drug monitoring required — trough should not exceed 1 mg/L (once daily) or 2 mg/L (multiple daily dosing); measure peak 1 hour after IV/IM bolus or 30 min after end of infusion; do not prescribe if serum concentrations cannot be monitored. Paediatric doses are stated in the SPC (children 1 year and above 3–6 mg/kg/day; infants after first month 4.5–7.5 mg/kg/day; neonates/pre-term 0–4 weeks 4–7 mg/kg/day) — verify paediatric dosing against a children's formulary.

Dose adjustments

Renal

In impaired renal function the daily dose must be decreased and adjusted to renal function (reduce dose and/or increase dose interval); monitor serum peak and trough concentrations and renal function frequently. SPC provides a multiple-daily-dose table by creatinine clearance (e.g. GFR 30–70 mL/min: 80 mg 12-hourly; 10–30 mL/min: 80 mg daily; use 60 mg if body weight under 60 kg).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any excipient
Myasthenia gravis

Side effects

Nephrotoxicity (usually reversible); acute renal failure (very rare)
Ototoxicity — transitory or irreversible hearing loss/deafness, particularly with renal dysfunction
Central and peripheral neuropathy (convulsions, lethargy, encephalopathy)
Hypersensitivity, anaphylaxis/anaphylactic reaction
Hypomagnesaemia on prolonged therapy

Interactions

Drugs that inhibit peristalsis should not be administered (risk of Clostridium difficile / pseudomembranous colitis)
Increased risk of ototoxicity in patients with mitochondrial DNA mutations (e.g. 1555 A>G in the 12S rRNA gene) — consider alternatives

Clinical monograph

How it works

It binds irreversibly to the bacterial 30S ribosomal subunit, causing misreading of mRNA and inhibition of protein synthesis, producing concentration-dependent bactericidal activity.

Prescribing in practice

Dose-related nephrotoxicity and irreversible ototoxicity (cochlear and vestibular) are the defining hazards, so therapy should be kept as short as possible with dosing and levels carefully managed, especially in renal impairment and the elderly.
Doses are calculated and adjusted using therapeutic drug monitoring against local protocols, often using ideal body weight in obesity.
Avoid concurrent nephrotoxic or ototoxic agents where possible, and use with particular caution in patients with myasthenia gravis.

Monitoring

Monitor serum gentamicin concentrations and renal function throughout treatment, with audiometry considered for prolonged courses.

Counselling the patient

Report any hearing loss, ringing in the ears, dizziness or unsteadiness immediately.
Regular blood tests are needed to keep the dose in the safe range.
Tell the team if you have kidney problems or any balance or hearing difficulties.

Evidence & guidelines

Gentamicin dosing and therapeutic drug monitoring are governed by national and local antimicrobial protocols to balance efficacy against nephrotoxicity and ototoxicity.

Reference: BSAC Endocarditis Guidelines; Hartford Nomogram; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

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