Antibiotic Eye Drops For Eye Infections

The general principles of management of infection in any part of the body also apply to the eye infection. An accurate diagnosis is necessary before selecting the most effective antibiotic. Most of the commercially available antibiotics are safe if used at proper concentration. 
However, higher concentrations and more number of applications than the prescribed limit may cause toxic effects like corneal epithelial defect and tear film instability.

The goal of achieving high antibiotic concentration in anterior segment can be achieved by frequent instillation of antibiotic eye drops into the lower conjunctival sac. Ophthalmic ointments have better retention time and hence better corneal penetration. Antibiotics exert their action by either killing the bacterial organism (bactericidal) or by inhibiting their multiplication (bacteriostatic). However, some bacteriostatic drugs become bactericidal when used in higher concentration as may occur with topical ophthalmic applications. Some of the ophthalmic antibiotics include the following;

• Ciprofloxacin, Ofloxacin, Norfloxacin and Gatifloxacin; They are generally called the fluroquinolones and are commercially available as 0.3% eye drops and 0.35 eye ointments. Topical fluroquinolones are effective in various infective conditions of the eye and are commonly used in treatment of bacterial conjunctivitis, keratitis, keratoconjunctivitis, blepharitis and dacryocystitis. They have good intraocular penetration and achieve adequate concentrations in aqueous humor. They kill the causative bacteria by attacking its DNA.

• Erythromycin; It is a bacteriostatic drug but becomes bactericidal in high concentration. Erythromycin is commercially available as 0.5% ointments which is indicated in neonatal conjunctivitis of the new born and in external bacterial infections of the eye. It also comes as a fortified eye drops (25mg/ml).

• Gentamycin and Tobramycin; They are commercially available as 0.3% eye drops, 0.3% ointment and as fortified eye drops (16-20mg/ml). They are used in the treatment of superficial eye infections like bacterial conjunctivitis. The eye drops achieve concentrations sufficient to treat superficial infections while fortified eye drops are required to achieve therapeutic levels consistently in the anterior chamber.

• Chloramphenicol; This is abacteriostatic antibiotics ideally suited for topical use in the eye (bacterial conjunctivitis) as it has least tendency to produce allergic reactions and has good corneal and intraocular penetration due to its high lipid solubility. It is commercially available as 0.5 or 1.0% eye drops, 0.5 or 1.0% eye ointments and as 5-10mg/ml fortified eye drops.

Other examples of ophthalmic antibiotics include the following;

Tetracyclines

Framycetin

Neomycin

Amikacin

Polymixin-B

Bacitracin

Fosfomycin

Vacomycin

Azithromycin

Lomefloxacin

Clarithromycin

Sparfloxacin

Basifloxacin

Levofloxacin

Moxifloxacin

Kenamycin

Sisomycin

Netilmicin

Siramycin

Etc.