Garamycin®

gentamicin 0.3% · ophthalmic solution

Antibiotic

Approved uses

Ocular bacterial infection: conjunctivitis, keratitis, keratoconjunctivitis, corneal ulcer, blepharitis, blepharoconjunctivitis, acute meibomianitis, dacryocystitis

1 to 2 drops into the affected eye(s) every 4 hours; up to 2 drops every hour in severe infection

OFF-LABELNot in the FDA label for this product

Bacterial keratitis treated with compounded fortified gentamicin 14 mg/mL (the concentration is off-label; keratitis itself is on-label at 0.3%)

Compounded gentamicin 14 mg/mL alternating with cefazolin 50 mg/mL, 1 drop of each every 5 minutes for the first 30 minutes as loading, then hourly on days 1 to 3, every 2 hours on days 4 to 6, every 4 hours on days 7 to 14

RCT · n=40 · surface toxicity

In a prospective double-masked randomized trial of 40 patients with presumed bacterial keratitis, fortified cefazolin 50 mg/mL plus gentamicin 14 mg/mL matched lomefloxacin 0.3% monotherapy: no significant difference in symptoms or signs at any visit, time to complete re-epithelialization P=0.251, healing by day 7 in 33% versus 44%. A separate double-masked randomized trial of 122 patients using fortified gentamicin 1.5% with cefuroxime 5% found similar cure within 14 days (67.9% versus 62.1% for ofloxacin; ratio 1.09, 95% CI 0.83 to 1.43) but five times more ocular surface toxicity (50.8% versus 10.2%; ratio 5.00, 95% CI 2.25 to 11.11).

Erjongmanee S, Kasetsuwan N, Phusitphoykai N, Puangsricharern V, Pariyakanok L. Clinical evaluation of ophthalmic lomefloxacin 0.3% in comparison with fortified cefazolin and gentamicin ophthalmic solutions in the treatment of presumed bacterial keratitis. J Med Assoc Thai. 2004;87 Suppl 2:S83-90 (PMID 16083168); Ofloxacin Study Group. Ofloxacin monotherapy for the primary treatment of microbial keratitis. Ophthalmology. 1997;104(11):1902-9 (PMID 9373124)

Contraindications

Known hypersensitivity to any component of the formulation.

Available Forms

0.3% (3 mg/mL) solution, 5 mL dropper bottle

Mechanism of Action

Aminoglycoside; actively transported into bacteria, where it binds the 30S ribosomal subunit and halts protein synthesis, giving concentration-dependent bactericidal killing. Labeled in vitro activity covers Pseudomonas aeruginosa, Serratia marcescens, Klebsiella pneumoniae, Escherichia coli, Enterobacter aerogenes, Haemophilus influenzae, Neisseria gonorrhoeae, staphylococci, and streptococci.

Warnings & Precautions

Route restriction: Never inject subconjunctivally or introduce directly into the anterior chamber.
Macular infarction: A survey of retinal specialists collected 93 cases attributed to gentamicin sulfate, and 23 cases across all aminoglycosides after prophylactic subconjunctival injection following routine ocular surgery.
Epithelial toxicity, fortified regimens: A fortified 1.5% solution with cefuroxime 5%, five times this product's concentration, caused corneal and conjunctival toxicity in 50.8% of eyes versus 10.2% on ofloxacin in a double-masked RCT of 122 patients with microbial keratitis (ratio 5.00, 95% CI 2.25 to 11.11).
Superinfection: Prolonged use may allow overgrowth of nonsusceptible organisms including fungi, and bacterial resistance may develop.
Hypersensitivity or worsening infection: Aggravated purulent discharge, inflammation, or pain, or irritation or hypersensitivity to any component, warrants stopping the drug and substituting appropriate therapy.

Common Side Effects

Ocular, most frequent: Burning and irritation on instillation, non-specific conjunctivitis, conjunctival epithelial defects, conjunctival hyperemia.
Corneal ulcers: Bacterial and fungal ulcers have developed during treatment with ophthalmic gentamicin preparations.
Rare reactions: Allergic reactions, thrombocytopenic purpura, hallucinations.

Pregnancy & Lactation

Pregnancy: No adequate and well-controlled studies in pregnant women; use only if the potential benefit justifies the potential fetal risk. Systemic dosing of pregnant rats at approximately 500 times the maximum recommended ophthalmic human dose depressed newborn body weights, kidney weights, and median glomerular counts.

Lactation: This label has no nursing mothers section.

Pediatric Use

≥2 months