TOBREX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TOBREX (TOBREX).
Tobramycin is an aminoglycoside antibiotic that irreversibly binds to the 30S ribosomal subunit, inhibiting protein synthesis and causing bacterial cell death.
| Metabolism | Minimal systemic absorption after ophthalmic administration; absorbed drug is primarily excreted unchanged by the kidneys via glomerular filtration. |
| Excretion | Primarily renal excretion of unchanged drug via glomerular filtration; approximately 60-80% recovered in urine within 8-12 hours. Biliary/fecal elimination accounts for less than 10%. |
| Half-life | Terminal elimination half-life: 2-3 hours in adults with normal renal function; prolonged to 24-36 hours in severe renal impairment (creatinine clearance <30 mL/min). |
| Protein binding | Approximately 10-20%; binding to plasma proteins is minimal. |
| Volume of Distribution | 0.25-0.4 L/kg; indicates distribution primarily into extracellular fluid with limited tissue penetration when administered topically; systemic exposure is negligible at ophthalmic doses. |
| Bioavailability | Ophthalmic administration: negligible systemic bioavailability (<1% absorbed via cornea and conjunctiva). No oral or parenteral formulations available. |
| Onset of Action | Ophthalmic solution: within 5 minutes; topical ophthalmic ointment: 15-30 minutes. No systemic routes approved. |
| Duration of Action | Ophthalmic solution: 6-8 hours; ophthalmic ointment: 8-12 hours. Duration may be reduced in severe infections. |
For bacterial conjunctivitis: 1-2 drops of 0.3% solution into affected eye(s) every 2-4 hours for 7-10 days. For severe infection: 2 drops every hour until improvement, then reduce to every 2-4 hours. Ointment: apply 0.5 inch ribbon twice daily for 7-10 days; for severe infection, every 3-4 hours until improvement.
| Dosage form | OINTMENT |
| Renal impairment | No dose adjustment required for any degree of renal impairment; negligible systemic absorption. |
| Liver impairment | No dose adjustment needed for any Child-Pugh class; negligible systemic absorption. |
| Pediatric use | Children ≥1 year: same as adult dosing. For bacterial conjunctivitis: 1-2 drops of 0.3% solution every 2-4 hours; ointment: 0.5 inch ribbon twice daily. Safety and efficacy not established in infants <1 year. |
| Geriatric use | No specific dose adjustment; use standard adult dosing. Monitor for local adverse effects as elderly may have increased risk of corneal epithelial defects or hypersensitivity. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TOBREX (TOBREX).
| Breastfeeding | Tobramycin is excreted into human milk in low concentrations after systemic administration. With ophthalmic use, systemic absorption is negligible, making significant infant exposure unlikely. M/P ratio not established for ophthalmic route. Use with caution. |
| Teratogenic Risk | Tobrex (tobramycin ophthalmic) is classified as Pregnancy Category D. Systemic absorption is minimal, but theoretical risk of ototoxicity and nephrotoxicity in the fetus. First trimester: avoid unless necessary. Second and third trimesters: use only if clearly needed; risk of fetal harm cannot be ruled out. |
■ FDA Black Box Warning
Ophthalmic only: No FDA boxed warning. Systemic tobramycin has boxed warnings for nephrotoxicity, ototoxicity, and neurotoxicity; not applicable to topical ophthalmic use.
| Serious Effects |
Hypersensitivity to tobramycin or any component of the formulation.
| Precautions | Prolonged use may result in overgrowth of nonsusceptible organisms including fungi; discontinue if superinfection occurs. Do not touch dropper tip to any surface to avoid contamination. Not for injection. Corneal epithelial toxicity with prolonged use. |
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| Fetal Monitoring | No special monitoring required due to minimal systemic absorption with ophthalmic use. If systemic toxicity suspected (prolonged use), monitor maternal renal function, hearing, and balance. |
| Fertility Effects | No known effects on fertility with ophthalmic use. Systemic aminoglycosides may impair fertility, but ophthalmic route has negligible systemic exposure. |