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Aminoglycoside Antibiotic — Ophthalmic Pregnancy: Topical use — considered low risk; minimal systemic absorption

Tobramycin Eye Drops 0.3% / Ointment

Brand names: Tobrex

Adult dose

Dose: 1–2 drops every 4 hours (drops); 1 cm ointment three times daily (ointment)
Route: Topical (ophthalmic)
Frequency: Every 4 hours (drops) or three times daily (ointment); hourly for severe keratitis
Max: 1–2 drops per dose
Ointment formulation preferred overnight for sustained coverage. Combined with dexamethasone in Tobradex for inflammatory bacterial conditions. Active against Pseudomonas aeruginosa and most Gram-negative bacteria.

Paediatric dose

Route: Topical
Frequency: Every 4–6 hours
Max: Same as adult
Used in paediatric bacterial eye infections; Tobradex (tobramycin + dexamethasone) has age restrictions — seek specialist guidance in children <2 years

Dose adjustments

Renal

No systemic absorption at topical doses — no adjustment required

Hepatic

No adjustment required

Clinical pearls

  • Pseudomonas aeruginosa keratitis: contact lens wearers are particularly susceptible — tobramycin or ciprofloxacin hourly (alternating) is the standard aggressive treatment; urgent ophthalmology referral mandatory
  • Tobradex (tobramycin 0.3% + dexamethasone 0.1%): used for blepharoconjunctivitis with inflammatory component — dexamethasone component is contraindicated if herpes simplex keratitis cannot be excluded; always confirm dendritic ulcers absent with fluorescein before prescribing
  • Ototoxicity/nephrotoxicity: NOT a concern with topical ophthalmic tobramycin — systemic absorption after topical application is negligible (naso-lacrimal drainage delivers small amounts to nasal mucosa but insufficient for systemic toxicity)
  • Bacterial conjunctivitis — Gram-negative predominant: tobramycin drops preferred over chloramphenicol in suspected Gram-negative infection (contact lens wearers, post-trauma)
  • Culture corneal scrapings before treatment for suspected bacterial keratitis — treatment should be guided by sensitivities when available

Contraindications

  • Hypersensitivity to tobramycin or other aminoglycosides
  • Herpes simplex keratitis (steroid component of Tobradex may worsen viral keratitis)

Side effects

  • Local irritation, stinging, burning
  • Eyelid pruritus and oedema
  • Conjunctival erythema
  • Blurred vision (ointment)

Interactions

  • Minimal systemic absorption — no clinically significant interactions

Monitoring

  • Response at 48 hours — if no improvement, reassess organism and sensitivities
  • Corneal integrity — fluorescein staining for ulceration

Reference: BNFc; BNF 90; RCOphth Microbial Keratitis Guidelines; SPC Tobrex; AAO Preferred Practice Pattern (Bacterial Keratitis). Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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