What is the recommended dose of gentamicin (antibiotic) for treating corneal abrasion?

Gentamicin Dosing for Corneal Abrasion

For corneal abrasion, gentamicin should be dosed as 1-2 drops into the affected eye every 4 hours, with severe infections requiring up to 2 drops every hour. 1

Standard Dosing Regimen

• The FDA-approved dosing for gentamicin ophthalmic solution is 1-2 drops instilled into the affected eye(s) every 4 hours for routine prophylaxis 1
• In severe infections or high-risk cases, the dosage may be increased to 2 drops every hour 1

Important Clinical Context

However, gentamicin is not the preferred antibiotic for corneal abrasion prophylaxis. The American Academy of Ophthalmology recommends fluoroquinolones (such as ofloxacin 0.3%, moxifloxacin 0.5%, or levofloxacin 1.5%) as the preferred broad-spectrum topical antibiotics for corneal abrasions, particularly in contact lens wearers who require Pseudomonas coverage 2, 3, 4

Why Fluoroquinolones Are Preferred Over Gentamicin

• Fluoroquinolones achieve superior corneal penetration compared to aminoglycosides like gentamicin 2
• Single-drug fluoroquinolone therapy has been shown to be as effective as combination fortified antibiotic therapy for corneal infections 3, 4
• Standard prophylaxis with fluoroquinolones involves applying drops 4 times daily until complete epithelial healing is confirmed, with treatment initiated within 24 hours of the abrasion 2

When Gentamicin Might Be Considered

• Gentamicin may be used as part of combination therapy with indomethacin for pain relief in traumatic corneal abrasions, dosed 4 times daily for 5-6 days 5
• Research suggests gentamicin penetration through normal human cornea is adequate for prophylaxis, though inferior to fluoroquinolones 6

Critical Caveats

• Contact lens wearers require fluoroquinolone coverage for Pseudomonas aeruginosa, making gentamicin alone inadequate for this high-risk population 3, 4
• Gentamicin-containing preparations with benzalkonium chloride may delay epithelial healing in reinjured corneas 7
• Treatment should be initiated within 24 hours of the abrasion to prevent ulceration 2, 4

Escalation for Severe Cases

• If the abrasion progresses to bacterial keratitis with central location, infiltrate >2mm, deep stromal involvement, or hypopyon, immediately escalate to loading doses of fluoroquinolones every 5-15 minutes, then hourly dosing 2
• Consider fortified antibiotics (tobramycin 1.5% + cefazolin 10%) for severe cases rather than continuing gentamicin monotherapy 2