Professional Information

Gentamicin (Topical)

VA CLASSIFICATION
Primary: DE101^{05}

Commonly used brand name(s): G-Myticin; Garamycin; Gentamar.

Note: For a listing of dosage forms and brand names by country availability, see Dosage Forms section(s).

Category:

Antibacterial (topical)—

Indications

Note: Bracketed information in the Indications section refers to uses that are not included in U.S. product labeling.

Accepted

Folliculitis (treatment)
Furunculosis (treatment)
Paronychia (treatment) or
Skin infections, bacterial, other minor (treatment)—Topical gentamicin is indicated in the topical treatment of folliculitis, furunculosis, paronychia, and other minor bacterial skin infections (including infected insect bites, infected minor burns, infected contact dermatitis, infectious eczematoid dermatitis, infected seborrheic dermatitis, infected excoriation, infected lacerations, infected skin abscesses and cysts, infected skin ulcers, infected stasis ulcers, infected stings, bacterial superinfections of minor fungal and viral infections, sycosis barbae, and minor surgical wounds) caused by staphylococci, streptococci, Proteus vulgaris , Escherichia coli , Pseudomonas aeruginosa , and Enterobacter aerogenes (Aerobacter aerogenes) . ^{03} ^{06} ^{21}

[Skin infections, bacterial, minor (prophylaxis)]¹or
[Ulcer, dermal (treatment)]—Topical gentamicin is used in the prophylaxis of minor bacterial skin infections and in the treatment of dermal ulcer. ^{01} ^{21}

—Not all species or strains of a particular organism may be susceptible to gentamicin.

Unaccepted
Indiscriminate use of topical gentamicin may lead to the emergence of aminoglycoside-resistant organisms. Therefore, use in immunocompromised or other high-risk patients is not recommended. ^{03}

Gentamicin is not effective against anaerobes, fungi, or viruses. ^{03} ^{04}

¹ Not included in Canadian product labeling.

Pharmacology/Pharmacokinetics

Physicochemical characteristics:

Chemical group—
Aminoglycosides. ^{15}

Mechanism of action/Effect:

Aminoglycoside; actively transported across the bacterial cell membrane, binds to a specific receptor protein on the 30 S subunit of bacterial ribosomes, and interferes with an initiation complex between mRNA (messenger RNA) and the 30 S subunit, inhibiting protein synthesis. DNA may be misread, thus producing nonfunctional proteins; polyribosomes are split apart and are unable to synthesize protein. ^{09}

Note: Aminoglycosides are bactericidal, while most other antibiotics that interfere with protein synthesis are bacteriostatic.

Absorption:

Although not absorbed through intact skin, topical gentamicin is readily absorbed from large denuded, burned, or granulating areas. Greater and more rapid absorption occurs with gentamicin cream than with the ointment. ^{15}

Precautions to Consider

Cross-sensitivity and/or related problems

Patients sensitive to one aminoglycoside may be sensitive to other aminoglycosides also. However, patients who are sensitive to neomycin have been treated with gentamicin without apparent adverse effects. ^{04}

Pregnancy/Reproduction

Problems in humans have not been documented.

Breast-feeding

It is not known whether topical gentamicin is distributed into breast milk. However, problems in humans have not been documented.

Pediatrics

Appropriate studies on the relationship of age to the effects of this medicine have not been performed in infants and children up to 1 year of age. In children over 1 year of age, appropriate studies performed to date have not demonstrated pediatrics-specific problems that would limit the usefulness of this medicine.

Geriatrics

Appropriate studies on the relationship of age to the effects of this medicine have not been performed in the geriatric population. However, no geriatrics-specific problems have been documented to date.

Medical considerations/Contraindications
The medical considerations/contraindications included have been selected on the basis of their potential clinical significance (reasons given in parentheses where appropriate)— not necessarily inclusive (» = major clinical significance).

Risk-benefit should be considered when the following medical problem exists
Sensitivity to topical gentamicin

Side/Adverse Effects
The following side/adverse effects have been selected on the basis of their potential clinical significance (possible signs and symptoms in parentheses where appropriate)—not necessarily inclusive:

Those indicating need for medical attention
Incidence less frequent

Hypersensitivity^{06} (itching, redness, swelling, or other sign of irritation not present before therapy)

Patient Consultation
As an aid to patient consultation, refer to Advice for the Patient, Gentamicin (Topical).

In providing consultation, consider emphasizing the following selected information (» = major clinical significance):

Before using this medication
»   Conditions affecting use, especially:
Sensitivity to aminoglycosides

Proper use of this medication
Before applying, washing affected area with soap and water and drying thoroughly; applying small amount and rubbing in gently

After applying, covering with gauze dressing if desired

» Compliance with full course of therapy

» Proper dosing
Missed dose: Applying as soon as possible; not applying if almost time for next dose

» Proper storage

Precautions while using this medication
Checking with physician if no improvement within 1 week

Side/adverse effects
Signs of potential side effects, especially hypersensitivity

General Dosing Information
The treated area(s) may be covered with a gauze dressing if desired. ^{06}

Serum concentrations up to 4 mcg per mL or more have been reported following topical administration. Nephrotoxicity and moderate to severe ototoxicity may occur, especially if renal function is impaired and systemic nephrotoxic and/or ototoxic drugs are given concurrently.

Use of topical antibacterials may lead to skin sensitization, resulting in hypersensitivity reactions with subsequent topical or systemic use of the medication.

Topical Dosage Forms

GENTAMICIN SULFATE CREAM USP

Usual adult and adolescent dose
Antibacterial
Topical, to the skin, three or four times a day. ^{06}

Usual pediatric dose
Antibacterial
Infants and children over 1 year of age: ^{04} See Usual adult and adolescent dose.

Strength(s) usually available
U.S.—

0.1% (base) (Rx) [Garamycin (butylparaben 0.4%) ( methylparaben 0.1%)] [Gentamar] [G-Myticin][Generic]^{06}^{07}^{12}

Canada—

0.1% (base) (Rx) [Garamycin (chlororesol 0.1%)]^{08}

Note: Each gram of cream contains 1.7 mg of gentamicin sulfate, equivalent to 1 mg of gentamicin base. ^{06} ^{16}

Packaging and storage:
Store below 40 °C (104 °F). Store in a collapsible tube or other tight container. Protect from freezing.

Auxiliary labeling:
   • For external use only.
   • Continue medication for full time of treatment.

Note: Gentamicin sulfate cream is water-washable and may be useful in treating wet, oozing primary infections and greasy, secondary infections of the skin, such as pustular acne or infected seborrheic dermatitis. ^{06}

GENTAMICIN SULFATE OINTMENT USP

Usual adult and adolescent dose
See Gentamicin Sulfate Cream USP. ^{06} ^{21}

Usual pediatric dose
See Gentamicin Sulfate Cream USP.

Strength(s) usually available
U.S.—

0.1% (base) (Rx) [Garamycin (methylparaben 0.05%) ( propylparaben 0.01%)] [Gentamar] [G-Myticin][Generic]^{06}^{07}^{14}

Canada—

0.1% (base) (Rx) [Garamycin (methylparaben 0.05%) (propylparaben 0.01%)]^{08}

Note: Each gram of ointment contains 1.7 mg of gentamicin sulfate, equivalent to 1 mg of gentamicin base. ^{06} ^{16}

Packaging and storage:
Store below 40 °C (104 °F). Store in a collapsible tube or other tight container. Protect from freezing.

Auxiliary labeling:
   • For external use only.
   • Continue medication for full time of treatment.

Note: Gentamicin sulfate ointment helps retain moisture and may be useful in treating infections of dry, eczematous, or psoriatic skin. ^{06}

Revised: 06/08/1994

References