Gentamicin is used topically in the treatment of superficial infections of the skin caused by susceptible bacteria. However, substantial evidence of effectiveness is lacking and some experts question the use of topical antibiotics in general. Minor skin infections and wounds usually heal without treatment, and systemic anti-infective therapy is required for the treatment of serious or extensive skin infections. In addition, indiscriminate use of topical gentamicin may result in the emergence of organisms resistant to the drug and other aminoglycosides.
For systemic uses of gentamicin, see 8:12.02. For use of gentamicin in infections of the eye, see 52:04.04.
Dosage and Administration
Gentamicin sulfate is applied topically to the skin in the form of a cream or ointment containing 0.1% gentamicin. Because the ointment helps retain moisture, it has been used in the treatment of infections on dry, eczematous, or psoriatic skin. The cream is usually used for the treatment of wet, oozing primary infections and greasy secondary infections; the cream is also used if a water-washable preparation is desired.
A small amount of gentamicin cream or ointment should be applied gently to the cleansed affected area 3-4 times daily. The area may be covered with a sterile gauze dressing; infected stasis ulcers may be covered with gelatin packing. In the topical treatment of impetigo, crusts should be removed from the lesions to permit contact between the antibiotic and the infection. Care should be taken to avoid further contamination of the infected skin.
Gentamicin appears to have a low order of toxicity when applied to the skin; however, sensitization to the drug may occasionally result from topical application. In addition, commercially available gentamicin preparations contain other ingredients such as parabens which may also cause allergic contact dermatitis. Local irritation including erythema and pruritus occur rarely following topical application of gentamicin. Possible photosensitization has been reported in several patients treated with topical gentamicin, but the reaction could not be directly attributed to the drug.
Precautions and Contraindications
The use of gentamicin may result in overgrowth of nonsusceptible organisms including fungi. If superinfection occurs during gentamicin therapy, the drug should be discontinued and appropriate therapy instituted.
Serious adverse reactions including ototoxicity and nephrotoxicity have occurred in patients receiving systemic gentamicin therapy. (See Cautions in the Aminoglycosides General Statement 8:12.02.) The possibility of cumulative toxicity should be considered if gentamicin is applied topically to large skin lesions or large areas of denuded skin in combination with systemic aminoglycoside therapy.
Topical gentamicin is contraindicated in patients who are hypersensitive to the drug or any ingredients in the formulations. Patients who are hypersensitive to other topical antibiotics should be closely observed during treatment with gentamicin. If irritation or hypersensitivity occurs, the drug should be discontinued. Cross-allergenicity among the aminoglycosides has been demonstrated and the possibility that patients who become sensitized to topical gentamicin may also be sensitive to other topical and/or systemic aminoglycosides should be considered.
Gentamicin sulfate is not usually absorbed following topical application to intact skin; however, the drug is readily absorbed through denuded areas of skin or skin that has lost the keratin layer as in wounds, burns, or ulcers. Greater absorption may occur with topical application of gentamicin cream than with topical application of gentamicin ointment.