Drug class: Antibacterials

Introduction

Antibacterial; aminoglycoside antibiotic obtained from cultures of Micromonospora purpurea.

Uses for Gentamicin (Topical)

Superficial Skin Infections

Topically to treat superficial skin infections caused by susceptible organisms.

Role of topical anti-infectives for treatment of superficial skin infections has not been fully elucidated.

Treatment of serious or extensive skin infections usually requires systemic anti-infective therapy.

Gentamicin (Topical) Dosage and Administration

General

• Consider location of the lesion and condition being treated when choosing a dosage form.

• Creams are suitable for wet, oozing primary infections and greasy secondary infections or if a water-washable preparation is needed.

• Ointments help retain moisture and are suitable for dry, eczematous, or psoriatic skin.

Administration

Topical Administration

Apply cream or ointment topically to the skin; avoid contact with eyes.

May cover affected area with a sterile bandage following use of ointment or cream.

When treating impetigo, remove lesion crusts before applying gentamicin; use care to avoid further contamination of the infected skin.

Manufacturer states infected stasis ulcers may be treated with gentamicin under gelatin packaging.

Dosage

Available as gentamicin sulfate; dosage expressed in terms of gentamicin.

Pediatric Patients

Superficial Skin Infections

Topical

Children ≥1 year of age: Apply a small amount to lesions 3–4 times daily.

Adults

Superficial Skin Infections

Topical

Apply a small amount to lesions 3–4 times daily.

Special Populations

No special population dosage recommendations at this time.

Cautions for Gentamicin (Topical)

Contraindications

• Known hypersensitivity to gentamicin or any ingredient in the formulation.

Warnings/Precautions

Sensitivity Reactions

Sensitization and photosensitivity reported following use of topical gentamicin.

Cross-Hypersensitivity

Cross-allergenicity occurs among the aminoglycosides; consider the possibility that patients who become sensitized to topical gentamicin may be sensitive to other topical and/or systemic aminoglycosides.

Closely observe patients hypersensitive to other topical antibiotics; discontinue gentamicin if irritation or hypersensitivity occurs.

General Precautions

Superinfection

Possible emergence and overgrowth of nonsusceptible bacteria or fungi. Discontinue drug and institute appropriate therapy if superinfection occurs.

Cumulative Toxicity

Possible cumulative toxicity if applied topically to large skin lesions or large areas of denuded skin in combination with systemic aminoglycoside therapy.

Specific Populations

Pregnancy

Category C.

Lactation

Not known whether gentamicin is distributed into milk following topical application; distributed into milk in small amounts following systemic administration.

AAP classifies gentamicin as compatible with breast-feeding.

Pediatric Use

Safety and efficacy not established in children <1 year of age.

Common Adverse Effects

Erythema, pruritus.

Gentamicin (Topical) Pharmacokinetics

Absorption

Bioavailability

Not usually absorbed from intact skin. Readily absorbed from denuded areas of skin or skin that has lost the keratin layer (i.e., wounds, burns, ulcers).

Greater absorption of gentamicin from cream than ointment.

Stability

Storage

Topical

Cream and Ointment

15–30°C.

Actions and Spectrum

• Usually bactericidal.

• Appears to inhibit protein synthesis in susceptible bacteria by irreversibly binding to 30S ribosomal subunits.

• Spectrum of activity includes many aerobic gram-negative bacteria and some aerobic gram-positive bacteria.

• Gram-positive aerobes: Active against Staphylococcus aureus. Minimally active against streptococci.

• Gram-negative aerobes: Active against Aerobacter aerogenes, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris, and Pseudomonas aeruginosa.

• Inactive against fungi, viruses, and most anaerobic bacteria.

• Resistance to gentamicin reported in both gram-positive and gram-negative bacteria. Partial cross-resistance occurs between gentamicin and other aminoglycosides.

Advice to Patients

• Importance of discontinuing gentamicin and instituting appropriate therapy if superinfection occurs.

• Importance of understanding that topical gentamicin preparations are for external use only; importance of not using in the eyes.

• Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.

• Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses.

• Importance of informing patients of other important precautionary information. (See Cautions.)

Additional Information

The American Society of Health-System Pharmacists, Inc. represents that the information provided in the accompanying monograph was formulated with a reasonable standard of care, and in conformity with professional standards in the field. Readers are advised that decisions regarding use of drugs are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and that the information contained in the monograph is provided for informational purposes only. The manufacturer’s labeling should be consulted for more detailed information. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information contained in the monograph is not a substitute for medical care.

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

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