Brand name: Tobrex
Drug class: Antibacterials
CAS number: 32986-56-4

Medically reviewed by Drugs.com on Oct 19, 2023. Written by ASHP.

Introduction

Antibacterial; aminoglycoside.^{1 2 6}

Uses for Tobramycin (EENT)

Bacterial Ophthalmic Infections

Topical treatment of superficial infections of the eye caused by susceptible bacteria.^{1 2 6}

Mild, acute bacterial conjunctivitis often resolves spontaneously without anti-infective treatment.^{135 136 137 141} Although topical ophthalmic anti-infectives may shorten time to resolution and reduce severity and risk of complications,^{135 136 137 141} avoid indiscriminate use of topical anti-infectives.^{135 141} Treatment of acute bacterial conjunctivitis generally is empiric;^{135 136 141} use of a broad-spectrum topical ophthalmic antibacterial usually recommended.^{135 136 141} 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.^{135 136 141}

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.¹³⁸ Treatment of community-acquired bacterial keratitis generally is empiric;¹³⁸ use of a broad-spectrum topical ophthalmic antibacterial usually recommended.¹³⁸ Subconjunctival anti-infectives may be necessary if scleral spread or perforation is imminent.¹³⁸ In vitro staining and/or cultures of corneal material are 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.¹³⁸

Ocular Inflammation

Fixed-combination ophthalmic preparations containing tobramycin and a corticosteroid (i.e., dexamethasone or loteprednol etabonate): Topical treatment of corticosteroid-responsive ocular conditions when a corticosteroid indicated and superficial bacterial ocular infection or risk of such infection exists.^{3 4 5 10 11}

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,^{3 4 5 10 11} experts state avoid use of such preparations in patients with bacterial conjunctivitis because of risk of potentiating the infection.¹³⁶

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.^{3 4 5 10 11} (See Use of Fixed Combinations Containing Corticosteroids under Cautions.)

Tobramycin (EENT) Dosage and Administration

Administration

Ophthalmic Administration

Apply tobramycin ophthalmic ointment or solution topically to the eye.^{1 2 3 6}

Apply fixed-combination ophthalmic ointment or suspensions containing tobramycin and a corticosteroid (i.e., dexamethasone or loteprednol) topically to the eye.^{3 4 5 10 11}

For topical ophthalmic use only;^{1 2 3 4 6 10 11} do not inject directly into eye.^{1 2 3 4 6 11}

Avoid contaminating container tip with material from any source.^{1 2 3 4 5 6 10 11}

Shake fixed-combination ophthalmic suspensions well prior to use.^{3 5 10 11}

Dosage

Pediatric Patients

Bacterial Ophthalmic Infections

Ophthalmic

Tobramycin 0.3% (ophthalmic ointment) in children ≥2 months of age: Apply approximately 1.25-cm (½-inch) ribbon in affected eye(s) 2 or 3 times daily.² For severe infections, apply to affected eye(s) every 3–4 hours initially.²

Tobramycin 0.3% (ophthalmic solution) in children ≥2 months of age: Instill 1 or 2 drops into affected eye(s) every 4 hours.^{1 6} For severe infections, instill 2 drops into affected eye(s) every hour initially.^{1 6}

When improvement occurs, taper dosage by decreasing frequency until drug is discontinued.^{1 2 6}

Usual duration of topical anti-infective treatment for bacterial conjunctivitis is 5–10 days;^{135 136 141} 5–7 days usually adequate for mild bacterial conjunctivitis.¹³⁵

Ocular Inflammation

Ophthalmic

Tobramycin 0.3% and dexamethasone 0.1% (ophthalmic ointment) in children ≥2 years of age: Apply approximately 1.25-cm (½-inch) ribbon into conjunctival sac of affected eye(s) up to 3 or 4 times daily.⁴

Tobramycin 0.3% and dexamethasone 0.05% (ophthalmic suspension) in children ≥2 years of age: Instill 1 or 2 drops into affected eye(s) every 4–6 hours.¹⁰ During initial 24–48 hours, 1 or 2 drops may be instilled every 2 hours if necessary.¹⁰

Tobramycin 0.3% and dexamethasone 0.1% (ophthalmic suspension) in children ≥2 years of age: Instill 1 or 2 drops into affected eye(s) every 4–6 hours.^{3 11} During initial 24–48 hours, 1 or 2 drops may be instilled every 2 hours if necessary.^{3 11}

If no improvement after 2 days, reevaluate patient.¹⁰ When improvement occurs, taper dosage by decreasing frequency until drug is discontinued.^{3 10 11} Do not discontinue prematurely.^{3 10 11}

Adults

Bacterial Ophthalmic Infections

Ophthalmic

Tobramycin 0.3% (ophthalmic ointment): Apply approximately 1.25-cm (½-inch) ribbon to affected eye(s) 2 or 3 times daily.² For severe infections, apply to affected eye(s) every 3–4 hours initially.²

Tobramycin 0.3% (ophthalmic solution): Instill 1 or 2 drops into affected eye(s) every 4 hours.^{1 6} For severe infections, instill 2 drops into affected eye(s) every hour initially.^{1 6}

When improvement occurs, taper dosage by decreasing frequency until drug is discontinued.^{1 2 6}

Usual duration of topical anti-infective treatment for bacterial conjunctivitis is 5–10 days;^{135 136 141} 5–7 days usually adequate for mild bacterial conjunctivitis.¹³⁵

Ocular Inflammation

Ophthalmic

Tobramycin 0.3% and dexamethasone 0.1% (ophthalmic ointment): Apply approximately 1.25-cm (½-inch) ribbon into conjunctival sac of affected eye(s) up to 3 or 4 times daily.⁴

Tobramycin 0.3% and dexamethasone 0.05% (ophthalmic suspension): Instill 1 or 2 drops into affected eye(s) every 4–6 hours.¹⁰ During initial 24–48 hours, 1 or 2 drops may be instilled every 2 hours if necessary.¹⁰

Tobramycin 0.3% and dexamethasone 0.1% (ophthalmic suspension): Instill 1 or 2 drops into conjunctival sac of affected eye(s) every 4–6 hours.^{3 11} During initial 24–48 hours, 1 or 2 drops may be instilled every 2 hours if necessary.^{3 11}

Tobramycin 0.3% and loteprednol etabonate 0.5% (ophthalmic suspension): Instill 1 or 2 drops into conjunctival sac of affected eye(s) every 4–6 hours.⁵ During initial 24–48 hours, 1 or 2 drops may be instilled every 1–2 hours if necessary.⁵

If no improvement after 2 days, reevaluate patient.^{5 10} When improvement occurs, taper dosage by decreasing frequency until drug is discontinued.^{3 5 10 11} Do not discontinue prematurely.^{3 5 10 11}

Cautions for Tobramycin (EENT)

Contraindications

• Tobramycin ophthalmic ointment or solution: Hypersensitivity to tobramycin or any ingredient in the formulation.^{1 2 6}

• Fixed-combination ophthalmic preparations containing tobramycin and a corticosteroid (i.e., dexamethasone or loteprednol): Known or suspected hypersensitivity to any ingredient in the formulation.^{3 4 10 11} Also, patients with viral diseases of the cornea and conjunctiva, including epithelial herpes simplex keratitis (dendritic keratitis), vaccinia, and varicella; mycobacterial infections of the eye; or fungal diseases of ocular structures.^{3 4 5 10 11}

Warnings/Precautions

Sensitivity Reactions

Hypersensitivity

Hypersensitivity reported.^{1 2 3 4 5 6} Sensitization to tobramycin may result from topical application.^{1 2 3 4 5 6 10 11}

Cross-allergenicity occurs among the aminoglycosides.^{1 2 3 4 5 6 11}

If sensitivity reaction occurs, immediately discontinue and initiate appropriate therapy.^{1 2 3 4 5 6 11}

Superinfection

Prolonged use may result in overgrowth of nonsusceptible organisms, including fungi.^{1 2 3 4 6 11}

If superinfection occurs, discontinue the drug and institute appropriate therapy.^{1 2 3 6 11}

Precautions Related to Ophthalmic Administration

If tobramycin is administered topically in conjunction with systemic aminoglycoside therapy, monitor serum aminoglycoside concentrations.^{1 2 3 6 10}

Manufacturers caution that ophthalmic ointments may delay corneal healing.^{2 4}

Do not wear contact lenses during treatment^{3 4 5 10 11} or if any signs or symptoms of bacterial ocular infection are present.^{2 4 6}

Use of Fixed Combinations Containing Corticosteroids

When ophthalmic preparations containing tobramycin in fixed combination with a corticosteroid (i.e., dexamethasone or loteprednol) used, consider cautions, precautions, and contraindications associated with EENT corticosteroids.^{3 4 5 10 11}

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 examining patient with slit lamp microscopy and, when appropriate, fluorescein staining.^{3 4 5 10 11}

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.^{3 4 5 10 11} If such preparation used for ≥10 days,^{5 10} routinely monitor IOP, even though this may be difficult in children and uncooperative patients.^{3 4 5 10 11} Use fixed combinations containing a corticosteroid with caution in patients with glaucoma; routinely check IOP in such patients.^{4 5 10 11}

Use of fixed-combination ophthalmic preparations containing a corticosteroid after cataract surgery may delay healing and increase incidence of bleb formation.^{3 4 5 10 11}

Use of topical corticosteroids in patients with thin corneal and scleral tissue may result in perforation.^{3 4 5 10 11}

Prolonged use of fixed-combination ophthalmic preparations containing a corticosteroid may suppress host responses and increase risk of secondary ocular infections.^{3 4 5 10 11} Use in patients with acute purulent conditions of the eye may mask infection or enhance existing infection.^{3 4 5 10 11}

May prolong course and exacerbate severity of many viral infections of the eye (including herpes simplex).^{5 10} Use with great caution in patients with herpes simplex.^{5 10}

Consider possibility of fungal infections of the cornea after prolonged use of ophthalmic preparations containing a corticosteroid.^{3 4 5 10 11} Perform fungal cultures when appropriate.⁵

Specific Populations

Pregnancy

No adequate and well-controlled studies using ophthalmic preparations containing tobramycin in pregnant women.^{1 2 3 4 5 6 10 11}

Use tobramycin ophthalmic ointment or solution during pregnancy only if clearly needed.^{1 2 6}

Use fixed-combination ophthalmic preparations containing tobramycin and a corticosteroid (i.e., dexamethasone or loteprednol etabonate) during pregnancy only if potential benefits justify potential risks to fetus.^{3 4 5 10 11}

Lactation

Discontinue nursing or the drug, taking into account importance of the drug to the woman.^{1 2 6}

Manufacturers state use fixed-combination ophthalmic preparations containing tobramycin and a corticosteroid with caution in nursing women.^{3 4 5 10 11}

Pediatric Use

Tobramycin ophthalmic ointment or solution: Safety and efficacy not established in children <2 months of age.^{1 2 6}

Fixed-combination ophthalmic preparations containing tobramycin and dexamethasone: Safety and efficacy not established in children <2 years of age.^{3 4 10 11}

Fixed-combination ophthalmic preparation containing tobramycin and loteprednol etabonate: Efficacy not established in pediatric patients.⁵

Geriatric Use

No overall differences in safety and efficacy observed between geriatric and younger adults.^{1 2 3 4 5 6 10 11}

Common Adverse Effects

Hypersensitivity and localized ocular toxicity (pruritus, edema of the eyelid, conjunctival erythema).^{1 2 6}

Tobramycin (EENT) Pharmacokinetics

Absorption

Extent

Absorbed into aqueous humor in rabbits following topical instillation of 0.3% solution in eye;^a not known if absorbed into vitreous humor following topical instillation.^a Absorption greatest when cornea is abraded.^a

Stability

Storage

Ophthalmic

Ointment

Tobramycin 0.3%: 2–25°C.²

Tobramycin 0.3% and dexamethasone 0.1%: 2–25°C.⁴

Solution

Tobramycin 0.3%: Depending on manufacturer, 2–25⁶ or 20–25°C;¹ protect from excessive heat.¹

Suspension

Tobramycin 0.3% and dexamethasone 0.05%: Store upright at 2–25°C;¹⁰ protect from light.¹⁰

Tobramycin 0.3% and dexamethasone 0.1%: Depending on manufacturer, store upright at 8–25³ or 20–25°C.¹¹

Tobramycin 0.3% and loteprednol etabonate 0.5%: Store upright at 15–25°C;⁵ protect from freezing.⁵

Actions and Spectrum

• Aminoglycoside antibiotic derived from cultures of Streptomyces tenebrarius.¹²

• Usually bactericidal.^a

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

• Spectrum of activity of tobramycin includes some aerobic gram-negative bacteria and some aerobic gram-positive bacteria.^{1 2 5 6} Inactive against Chlamydia, fungi, viruses, and most anaerobic bacteria.^a

• Gram-positive bacteria: Active in vitro against some Staphylococcus aureus, S. epidermidis, Streptococcus pneumoniae, and group A β-hemolytic streptococci.^{1 2 6}

• Gram-negative bacteria: Active in vitro against some Acinetobacter calcoaceticus, Haemophilus influenzae, H. aegyptius, Enterobacter aerogenes, Escherichia coli, Klebsiella pneumoniae, Moraxella lacunata, Morganella morganii, Neisseria, Proteus mirabilis, P. vulgaris, and Pseudomonas aeruginosa.^{1 2 6}

• Natural and acquired resistance to tobramycin demonstrated in both gram-negative and gram-positive bacteria.^a

• Partial cross-resistance occurs between tobramycin and other aminoglycosides.^a

• Advise patients to avoid contaminating container tip with material from any source.^{1 2 3 4 5 6}

• Advise patients not to wear contact lenses during treatment^{3 4 5 10 11} or if they have signs and symptoms of bacterial ocular infection.^{2 4 6}

• Advise patients to contact a clinician if pain develops or if redness, itching, or inflammation becomes aggravated.⁵

• Importance of patients informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses.^{1 2 3 4 5 5 6 10 11}

• Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.^{1 2 3 4 5 5 6 10 11}

• Importance of informing patients of other important precautionary information.^{1 2 3 4 5 6 10 11} (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

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