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Topical Aminoglycoside — Otitis Externa Pregnancy: Safety for use in pregnancy and lactation has not been established. Gentamicin should only be used in pregnancy or lactation when considered essential by the physician, after careful assessment of the potential risks and benefits.

Gentamicin Ear Drops

Brand names: Genticin Ear Drops, Cidomycin

Used in: Acute Appendicitis

Gentamicin ear drops are a topical aminoglycoside antibiotic preparation, often combined with a corticosteroid, used to treat bacterial infections of the outer ear (otitis externa).

Adult dose

Dose: Otitis externa: after cleansing the area, 2-3 drops of gentamicin 0.3% w/v solution instilled in the affected ear 3-4 times a day and at night, or more frequently if required
Route: Otic - drops instilled in the affected ear (this card does not cover the eye route of the same product)
Frequency: 3-4 times a day and at night, or more frequently if required
Pinned product: Gentamicin Eye/Ear Drops 0.3% w/v (eMC product 4218); SPC section 2: "Gentamicin sulphate equivalent to 30mg gentamicin base in 10ml of solution" (benzalkonium chloride 0.10mg/ml). SPC 4.1 verbatim: "Also indicated for the treatment of otitis externa." (the product's main indications are external eye infections). SPC 4.2 verbatim: "Adults, including the elderly and children ... Ears : The area should be cleansed and 2-3 drops instilled in the affected ear 3-4 times a day and at night or more frequently if required." The eye regimen is not covered by this card. SPC 4.3: contraindicated with a perforated tympanic membrane. SPC 4.4: "The condition of the ear drum must always be checked before this medicinal product is prescribed. The medicinal product must not be used if the integrity of the ear drum cannot be guaranteed. Irreversible toxic effects may result from direct contact of gentamicin with the middle and inner ear." "Avoid prolonged use." "In severe infections, topical use of gentamicin should be supplemented with appropriate systemic antibiotic treatment." SPC 4.8: "In the event of irritation, sensitivity or super-infection, treatment should be discontinued and appropriate therapy instituted." The SPC prints no maximum dose or duration.

Paediatric dose

Route: Otic - drops instilled in the affected ear
Frequency: 3-4 times a day and at night, or more frequently if required
SPC 4.2 verbatim: "Adults, including the elderly and children ... Ears : The area should be cleansed and 2-3 drops instilled in the affected ear 3-4 times a day and at night or more frequently if required." No age bands, lower age limit or per-kg figure are printed - do not derive one. Same eardrum-integrity precautions apply (SPC 4.3, 4.4).

Dose adjustments

Renal

No dose adjustment is stated in SPC 4.2. SPC 4.4: ototoxicity (when given systemically or applied topically to open wounds or damaged skin) is dose-related and is enhanced by renal and/or hepatic impairment and is more likely in the elderly.

Hepatic

No dose adjustment is stated in SPC 4.2. SPC 4.4: ototoxicity (when given systemically or applied topically to open wounds or damaged skin) is dose-related and is enhanced by renal and/or hepatic impairment and is more likely in the elderly.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Hypersensitivity to the active substance, gentamicin, or to any of the excipients listed in section 6.1
  • Known allergy to gentamicin and other aminoglycosides
  • Myasthenia gravis and related conditions (gentamicin may cause neuromuscular blockade)
  • Perforated tympanic membrane

Side effects

  • Ear and labyrinth disorders: local sensitivity; ototoxicity; vestibular disorder; hearing loss
  • Skin and subcutaneous tissue disorders: burning sensation, stinging, itching (pruritus); dermatitis
  • Eye disorders (eye use): local sensitivity, blurred vision, eye irritation, burning sensation, stinging sensation, itching
  • Nephrotoxicity may occur when gentamicin is given systemically; systemic absorption after topical use is likely not a comparable risk
  • All listed effects are of frequency unknown (no modern clinical studies available)

Interactions

  • Potent diuretics such as ethacrynic acid and frusemide: believed to enhance any risk of ototoxicity
  • Amphotericin B, cisplatin, cyclosporin and cephalosporins: potential enhancers of nephrotoxicity
  • Other potentially nephrotoxic or ototoxic drugs: avoid concurrent use unless considered essential by the physician
  • Curare-type muscle relaxants given during anaesthesia: neuromuscular blockade and respiratory paralysis have been reported with aminoglycosides
  • Systemic aminoglycosides: caution advised when used concomitantly

Monitoring

  • Condition of the ear drum must always be checked before prescribing; do not use if the integrity of the ear drum cannot be guaranteed
  • Avoid prolonged use (skin sensitisation and emergence of resistant organisms)
  • Ototoxicity (vestibular damage; irreversible partial or total deafness), including increased risk in patients with mitochondrial mutations, particularly m.1555A>G, even when serum levels are within the recommended range
  • Irritation, sensitivity or super-infection: discontinue treatment and institute appropriate therapy

Clinical monograph

How it works

Gentamicin binds irreversibly to the bacterial 30S ribosomal subunit, inhibiting protein synthesis and producing a bactericidal effect against many Gram-negative organisms.

Prescribing in practice

  • Aminoglycoside ear drops are potentially ototoxic and should be avoided where the tympanic membrane is perforated, as access to the middle ear risks vestibular and cochlear damage.
  • Reserved for use when the eardrum is known to be intact unless a specialist judges the benefit to outweigh the ototoxicity risk.
  • Prolonged or repeated courses may encourage fungal or resistant bacterial superinfection of the ear canal.

Monitoring

Monitor for resolution of infection and for any new hearing loss, tinnitus or vertigo, which warrant immediate discontinuation and review.

Counselling the patient

  • Tell us straight away if you notice any change in hearing, ringing in the ears, or dizziness.
  • Stop using the drops and seek advice if symptoms worsen or fail to settle.
  • Use only for the duration advised and do not continue beyond the recommended course.

Evidence & guidelines

Use is guided by NICE and MHRA advice on the ototoxicity risk of topical aminoglycosides in the presence of a perforated eardrum.

Reference: NICE CKS Otitis Externa; ENT-UK CSOM Guidelines; BSO Menière's Disease Guidelines; 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).

Related

Curated clinical cross-links plus same-class fallbacks.

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