Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Ointment, Ophthalmic:
Tobrex: 0.3% (3.5 g)
Solution, Ophthalmic:
Tobrex: 0.3% (5 mL)
Generic: 0.3% (5 mL)
Pharmacology
Mechanism of Action
Interferes with bacterial protein synthesis by binding to 30S ribosomal subunit resulting in a defective bacterial cell membrane
Pharmacokinetics/Pharmacodynamics
Absorption
Systemic absorption: Undetectable (<0.2 mcg/mL) (Filatov 1994); tear film exposure and time above MIC90 are significantly greater with viscous ophthalmic solution [Canadian product] (Tobrexan Canadian product labeling 2016).
Use: Labeled Indications
Ocular infections: Treatment of external infections of the eye and its adnexa caused by susceptible bacteria.
Contraindications
Hypersensitivity to tobramycin or any component of the formulation
Canadian labeling: Additional contraindications (not in US labeling): Known hypersensitivity to any aminoglycoside
Dosage and Administration
Dosing: Adult
Ocular infections: Ophthalmic:
Ointment: Apply half-inch ribbon into affected eye(s) 2 or 3 times daily for mild to moderate infections; for severe infections, apply every 3 to 4 hours until improvement (then reduce prior to discontinuation).
Solution: Instill 1 to 2 drops into affected eye(s) every 4 hours for mild to moderate infections; for severe infections, instill 2 drops every hour until improvement (then reduce prior to discontinuation).
Viscous solution (Tobrexan [Canadian product]): Instill 1 drop into affected eye(s) 2 times daily for 7 days for mild to moderate infections; for severe infections, instill 1 drop 4 times daily on day 1 and then 2 times daily for duration of treatment period.
Dosing: Pediatric
Ocular infections: Ophthalmic: Infants ≥2 months, Children, and Adolescents:
Ointment:
Mild to moderate infections: Apply 1/2 inch ribbon into the affected eye(s) 2 to 3 times daily
Severe infections: Apply 1/2 inch ribbon into the affected eye(s) every 3 to 4 hours initially until improvement, then reduce to less frequent intervals prior to discontinuation
Solution:
Mild to moderate infections: Instill 1 to 2 drops into the affected eye(s) every 4 hours
Severe infections: Instill 2 drops into the affected eye(s) every hour initially until improvement, then reduce to less frequent intervals prior to discontinuation
Administration
For topical ophthalmic use only; not for injection into the eye. Contact lenses should not be worn during treatment of ophthalmic infections. Avoid contaminating the applicator tip with affected eye(s).
Ointment: Apply into conjunctival sac(s) of eye; patient should look downward before closing eye.
Storage
Store at 2°C to 25°C (36°F to 77°F).
Drug Interactions
There are no known significant interactions.
Adverse Reactions
<1%, postmarketing, and/or case reports: Conjunctival erythema, eyelid edema, eyelid pruritus
Warnings/Precautions
Concerns related to adverse effects:
- Hypersensitivity reactions: Sensitivity to topically applied aminoglycosides and cross sensitivity to other aminoglycosides antibiotics may occur; discontinue use if hypersensitivity develops.
- Superinfection: Prolonged use may lead to overgrowth of nonsusceptible organisms, including fungi. If superinfection is suspected, institute appropriate alternative therapy.
Special populations:
- Contact lens wearers: Some products may contain benzalkonium chloride or benzododecinium bromide which may be absorbed by soft contact lenses; contact lenses should not be worn during treatment of ophthalmologic infections.
Other warnings/precautions:
- Appropriate use: For topical application to the eye only; not for injection. To avoid contamination, do not touch tip of container to any surface.
Pregnancy
Pregnancy Risk Factor
B
Pregnancy Considerations
Adverse events have not been observed in animal reproduction studies. The amount of tobramycin available systemically following topical application of the ophthalmic drops is undetectable (<0.2 mcg/mL) (Filatov 1994). If ophthalmic agents are needed during pregnancy, the minimum effective dose should be used in combination with punctal occlusion to decrease systemic absorption (Samples 1988).
Patient Education
What is this drug used for?
- It is used to treat eye infections.
Other side effects of this drug: Talk with your doctor right away if you have any of these signs of:
- Vision changes
- Eye pain
- Severe eye irritation
- Signs of a significant reaction like wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat.
Note: This is not a comprehensive list of all side effects. Talk to your doctor if you have questions.
Consumer Information Use and Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only the healthcare provider has the knowledge and training to decide which medicines are right for a specific patient. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this medicine. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not specific medical advice and does not replace information you receive from the healthcare provider. You must talk with the healthcare provider for complete information about the risks and benefits of using this medicine.
