From the Guidelines
Gentamicin ophthalmic solution should be prepared by withdrawing 2 ml from an injectable vial of intravenous gentamicin (40 mg/ml) and adding it to a 5-ml bottle to give a 14 mg/ml solution, as recommended by the bacterial keratitis preferred practice pattern 1. To prepare the solution, follow these steps:
- Withdraw 2 ml from an injectable vial of intravenous gentamicin (40 mg/ml)
- Add the withdrawn 2 ml to a 5-ml bottle of gentamicin ophthalmic solution to give a 14 mg/ml solution
- Refrigerate and shake well before instillation 1 When administering the prepared gentamicin ophthalmic solution, patients should tilt their head back, pull down the lower eyelid to form a pocket, instill the medication, close the eye gently for 1-2 minutes, and apply gentle pressure to the inner corner of the eye to prevent systemic absorption. It is essential to note that gentamicin works by inhibiting bacterial protein synthesis, making it effective against many gram-negative and some gram-positive bacteria 1. However, it is not effective against viral or fungal infections, so proper diagnosis is essential before initiating treatment. The treatment duration should generally continue for 7-10 days, even if symptoms improve earlier, to ensure complete eradication of the infection. For conjunctivitis or minor external eye infections, instill 1-2 drops of the prepared solution into the affected eye(s) every 4 hours while awake. For more severe infections, dosing may be increased to every 2 hours initially, then tapered as improvement occurs.
From the FDA Drug Label
Gentamicin sulfate ophthalmic solution, USP is indicated in the topical treatment of ocular bacterial infections including conjunctivitis, keratitis, keratoconjunctivitis, corneal ulcers, blepharitis, blepharoconjunctivitis, acute meibomianitis, and dacryocystitis, caused by susceptible strains of the following microorganisms: Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, Streptococcus pneumoniae, Enterobacter aerogenes, Escherichia coli, Haemophilus influenzae, Klebsiella pneumoniae, Neisseria gonorrhoeae, Pseudomonas aeruginosa, and Serratia marcescens. The FDA drug label does not answer the question about suggested guidelines for gentamicin ophthalmic gtts/ointment for eyes, as it only provides information on indications, contraindications, and storage, but not on usage guidelines 2, 2, 2.
From the Research
Suggested Guidelines for Gentamicin Ophthalmic Drops/Ointment for Eyes
- The effectiveness and safety of gentamicin ophthalmic solution were compared with those of 0.3% ofloxacin solution in treating external bacterial ocular infections, with a clinical improvement rate of 92% for gentamicin 3.
- Gentamicin ointment was used in a study to compare the efficacy of antibiotic drops placed in the conjunctival cul-de-sac to antibiotic ointment applied to the lid margin in reduction of bacterial colonization on the lid margin, with no statistically significant difference between antibiotic drop and ointment 4.
- Aminoglycosides, including gentamicin, are broad-spectrum antibacterials, but the widespread use of an antibacterial increases risks of selecting resistance to it 5.
- Gentamicin was tested for its susceptibility to ocular bacterial isolates of clinically symptomatic eyes, with an overall in vitro efficacy lower than that of chloramphenicol, ciprofloxacin, ofloxacin, and norfloxacin 6.
- A multicenter study compared the efficacy of topical tobramycin and gentamicin sulfate in the treatment of ocular infections, with tobramycin being significantly more effective than gentamicin sulfate clinically and exhibiting a greater antibacterial efficacy 7.
Key Points to Consider
- Gentamicin is effective against a range of bacterial infections, but its use should be considered in the context of potential resistance and side effects 3, 5, 6, 7.
- The choice of antibacterial agent depends on various factors, including pharmacodynamic, pharmacokinetic, and bacteriological characteristics, as well as cost and potential side effects 5.
- Gentamicin ointment may be associated with a higher frequency of adverse reactions compared to other antibacterial agents, such as tobramycin 7.