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Gentamicin (EENT)

Class: Antibacterials
VA Class: AM300
CAS Number: 1405-41-0
Brands: Gentak

Medically reviewed by Drugs.com on Oct 19, 2021. Written by ASHP.

Introduction

Antibacterial; aminoglycoside.

Uses for Gentamicin (EENT)

Bacterial Ophthalmic Infections

Topical treatment of superficial bacterial infections of the eye caused by susceptible bacteria, including Staphylococcus aureus, S. epidermidis, Streptococcus pyogenes, S. pneumoniae, Enterobacter aerogenes, Escherichia coli, Haemophilus influenzae, Klebsiella pneumoniae, Neisseria gonorrhoeae, Serratia marcescens, and Pseudomonas aeruginosa.

Mild, acute bacterial conjunctivitis often resolves spontaneously without anti-infective treatment. Although topical ophthalmic anti-infectives may shorten time to resolution and reduce severity and risk of complications, avoid indiscriminate use of topical anti-infectives. Treatment of acute bacterial conjunctivitis generally is empiric; use of a broad-spectrum topical ophthalmic antibacterial usually recommended. In vitro staining and/or cultures of conjunctival material may be indicated in management of recurrent, severe, or chronic purulent conjunctivitis or when acute conjunctivitis does not respond to initial empiric topical treatment.

Because bacterial keratitis may be associated with subsequent loss of vision as the result of corneal scarring or topographic irregularities and because untreated or severe bacterial keratitis may result in corneal perforation with potential for endophthalmitis and possible loss of the eye, optimal management involves rapid evaluation and diagnosis, timely initiation of treatment, and appropriate follow-up. Treatment of community-acquired bacterial keratitis generally is empiric; use of a broad-spectrum topical ophthalmic antibacterial usually recommended. Subconjunctival anti-infectives may be necessary if scleral spread or perforation is imminent. In vitro staining and/or cultures of corneal material indicated in management of keratitis involving corneal infiltrates that are central, large, and extend to the middle to deep stroma; when keratitis is chronic or unresponsive to a broad-spectrum topical anti-infective; or when atypical features suggest fungal, amebic, or mycobacterial infection.

Ocular Inflammation

Fixed-combination ophthalmic preparations containing gentamicin and a corticosteroid (i.e., prednisolone): Topical treatment of corticosteroid-responsive ocular conditions when a corticosteroid indicated and superficial bacterial ocular infection or risk of such infection exists.

Although manufacturers state that use of a fixed-combination ophthalmic preparation containing an anti-infective and a corticosteroid may be indicated in ocular inflammatory conditions when risk of superficial ocular infection is high or when potentially dangerous numbers of bacteria are expected to be present in the eye, experts state avoid use of such preparations in patients with bacterial conjunctivitis because of risk of potentiating the infection.

Consider that use of fixed-combination ophthalmic preparations containing an anti-infective and a corticosteroid may mask clinical signs of bacterial, fungal, or viral infections; prevent recognition of ineffectiveness of the anti-infective; and/or increase IOP. (See Use of Fixed combinations Containing Corticosteroids under Cautions.)

Gentamicin (EENT) Dosage and Administration

Administration

Ophthalmic Administration

Apply gentamicin ophthalmic ointment or solution topically to the eye.

Apply fixed-combination ophthalmic ointment or suspension containing gentamicin and a corticosteroid (i.e., prednisolone) topically to the eye.

For topical ophthalmic use only; do not inject subconjunctivally or directly into anterior chamber of the eye.

Avoid contaminating container tip with material from eye, eyelid, or any other source.

Shake fixed-combination ophthalmic suspension well prior to use.

Dosage

Available as gentamicin sulfate alone or in fixed combination with prednisolone acetate. Dosage of gentamicin expressed in terms of the base; dosage of prednisolone acetate expressed in terms of the salt.

Pediatric Patients

Bacterial Ophthalmic Infections
Ophthalmic

Gentamicin 0.3% (ophthalmic ointment) in pediatric patients ≥1 month of age: Apply approximately 1.25-cm (½-inch) ribbon in affected eye(s) 2 or 3 times daily.

Gentamicin 0.3% (ophthalmic solution) in pediatric patients ≥1 month of age: Instill 1 or 2 drops into affected eye(s) every 4 hours. For severe infections, up to 2 drops may be instilled every hour.

Usual duration of topical anti-infective treatment for bacterial conjunctivitis is 5–10 days; 5–7 days usually adequate for mild bacterial conjunctivitis.

Adults

Bacterial Ophthalmic Infections
Ophthalmic

Gentamicin 0.3% (ophthalmic ointment): Apply approximately 1.25-cm (½-inch) ribbon in affected eye(s) 2 or 3 times daily.

Gentamicin 0.3% (ophthalmic solution): Instill 1 or 2 drops into affected eye(s) every 4 hours. For severe infections, up to 2 drops may be instilled every hour.

Usual duration of topical anti-infective treatment for bacterial conjunctivitis is 5–10 days; 5–7 days usually adequate for mild bacterial conjunctivitis.

Ocular Inflammation
Ophthalmic

Gentamicin 0.3% and prednisolone acetate 0.6% (ophthalmic ointment): Apply approximately 1.25-cm (½-inch) ribbon into conjunctival sac of affected eye(s) 1–3 times daily.

Gentamicin 0.3% and prednisolone acetate 1% (ophthalmic suspension): Instill 1 drop into conjunctival sac of affected eye(s) 2–4 times daily. During initial 24–48 hours, 1 drop may be instilled every hour if necessary.

If no improvement after 2 days, reevaluate patient. Do not discontinue prematurely.

Cautions for Gentamicin (EENT)

Contraindications

  • Gentamicin ophthalmic ointment or solution: Hypersensitivity to gentamicin or any ingredient in the formulation.

  • Fixed-combination ophthalmic preparations containing gentamicin and a corticosteroid (i.e., prednisolone): Known or suspected hypersensitivity to gentamicin, prednisolone or other corticosteroids, or any ingredient in the formulation. Also, patients with viral diseases of the cornea and conjunctiva, including epithelial herpes simplex keratitis (dendritic keratitis), vaccinia, and varicella; with mycobacterial infections of the eye; or fungal diseases of ocular structures.

Warnings/Precautions

Sensitivity Reactions

Hypersensitivity

Allergic reactions reported.

If hypersensitivity occurs, immediately discontinue and initiate appropriate therapy.

Superinfection

Prolonged use may result in overgrowth of nonsusceptible organisms, including fungi.

Bacterial resistance to gentamicin may occur.

Bacterial and fungal corneal ulcers have developed.

Precautions Related to Ophthalmic Administration

Manufacturer cautions that ophthalmic ointments may delay corneal healing.

Use of Fixed Combinations Containing Corticosteroids

When ophthalmic preparations containing gentamicin in fixed combination with a corticosteroid (i.e., prednisolone) used, consider cautions, precautions, and contraindications associated with EENT corticosteroids.

Provide initial prescriptions for fixed-combination ophthalmic preparations containing a corticosteroid or renewal prescriptions (beyond 8 g of ophthalmic ointment or beyond 20 mL of ophthalmic solution) only after measuring IOP and examining patient with slit lamp microscopy and, when appropriate, fluorescein staining.

Prolonged use of fixed-combination ophthalmic preparations containing a corticosteroid may result in glaucoma, with optic nerve damage, defects in visual acuity and fields of vision, and posterior subcapsular cataract formation. If such preparation used for ≥10 days, routinely monitor IOP, even though this may be difficult in children and uncooperative patients. Use fixed combinations containing a corticosteroid with caution in patients with glaucoma; check IOP frequently in such patients.

Use of fixed-combination ophthalmic preparations containing a corticosteroid after cataract surgery may delay healing and increase incidence of bleb formation.

Corneal and scleral thinning reported with various ocular diseases and with long-term use of topical corticosteroids. Use of topical corticosteroids in patients with thin corneal and scleral tissue may result in perforation.

Prolonged use of fixed-combination ophthalmic preparations containing a corticosteroid may suppress host responses and increase risk of secondary ocular infections. Use in patients with acute purulent conditions of the eye may mask infection or enhance existing infection.

May prolong course and exacerbate severity of many viral infections of the eye (including herpes simplex). Use with great caution in patients with herpes simplex; frequent slit lamp microscopy recommended.

Consider possibility of fungal infections of the cornea after prolonged use of ophthalmic preparations containing a corticosteroid. Perform fungal cultures when appropriate.

Specific Populations

Pregnancy

No adequate and well-controlled studies using ophthalmic preparations containing gentamicin in pregnant women.

Use gentamicin ophthalmic preparations, including fixed-combination preparations containing gentamicin and a corticosteroid, during pregnancy only if potential benefits justify potential risks to fetus.

Lactation

Systemic gentamicin is distributed into milk.

Discontinue nursing or the drug, taking into account importance of the drug to the woman.

Pediatric Use

Gentamicin ophthalmic ointment or solution: Safety and efficacy not established in neonates.

Fixed-combination ophthalmic preparations containing gentamicin and a corticosteroid (i.e., prednisolone): Safety and efficacy not established in pediatric patients.

Geriatric Use

Fixed-combination ophthalmic preparations containing gentamicin and prednisolone: No overall differences in safety or efficacy relative to younger adults.

Common Adverse Effects

Ocular burning and irritation, nonspecific conjunctivitis, conjunctival epithelial defects, conjunctival hyperemia.

Gentamicin (EENT) Pharmacokinetics

Absorption

Extent

Studies in rabbits suggest that gentamicin is absorbed into aqueous humor following topical application of the ophthalmic ointment or solution to the eye; also detected in vitreous humor. Absorption greatest when cornea is abraded.

Distribution

Extent

Systemic gentamicin crosses the placenta and is distributed into breast milk.

Stability

Storage

Ophthalmic

Ointment

Gentamicin 0.3%: 2–30°C.

Gentamicin 0.3% and prednisolone acetate 0.6%: 15–25°C.

Solution

Gentamicin 0.3%: 20–25°C; avoid excessive heat.

Suspension

Gentamicin 0.3% and prednisolone acetate 1%: 15–25°C. Do not freeze; protect from excessive heat (≥40°C).

Actions and Spectrum

  • Aminoglycoside antibiotic obtained from cultures of Micromonospora purpurea.

  • Usually bactericidal.

  • Mechanism of action not fully elucidated; appears to inhibit protein synthesis in susceptible bacteria by irreversibly binding to 30S ribosomal subunits.

  • Spectrum of activity of gentamicin includes many aerobic gram-negative and some aerobic gram-positive bacteria. Inactive against fungi, viruses, and most anaerobic bacteria.

  • Gram-positive bacteria: Active in vitro against Staphylococcus aureus, S. epidermidis, Streptococcus pneumoniae, and S. pyogenes.

  • Gram-negative bacteria: Active in vitro against Haemophilus influenzae, Enterobacter aerogenes, Escherichia coli, Klebsiella pneumoniae, Neisseria gonorrhoeae, Serratia marcescens, and Pseudomonas aeruginosa.

  • Natural and acquired resistance to gentamicin demonstrated in both gram-negative and gram-positive bacteria.

  • Partial cross-resistance occurs between gentamicin and other aminoglycosides.

Advice to Patients

  • Advise patients to avoid contaminating container tip with material from eye, eyelid, or any other source. Keep container tightly closed when not in use; do not share with others.

  • Advise patients to immediately discontinue gentamicin ophthalmic preparation and contact a clinician if irritation or hypersensitivity occurs. Also discontinue and contact a clinician if there is an increase in purulent discharge or aggravation of inflammation or pain.

  • Advise patients using fixed-combination ophthalmic preparation containing a corticosteroid to discontinue the drug and contact a clinician if inflammation or pain persists for >48 hours or becomes aggravated.

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

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

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

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

Gentamicin Sulfate

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Ophthalmic

Ointment

0.3% (of gentamicin)*

Gentak

Akorn

Gentamicin Sulfate Ophthalmic Ointment

Solution

0.3% (of gentamicin)*

Gentak

Akorn

Gentamicin Sulfate Ophthalmic Solution

Gentamicin Sulfate and Prednisolone Acetate

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Ophthalmic

Ointment

Gentamicin Sulfate 0.3% (of gentamicin) and Prednisolone Acetate 0.6%

Pred-G

Allergan

Suspension

Gentamicin Sulfate 0.3% (of gentamicin) and Prednisolone Acetate 1%

Pred-G

Allergan

AHFS DI Essentials™. © Copyright 2022, Selected Revisions October 29, 2018. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.

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