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. |
| Molecular Weight | 467.5 |
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 | Safety not established; limited human data. Ophthalmic use may minimize systemic exposure. Use only if clearly needed. |
| 2nd trimester | No known teratogenic effects in animal studies; ophthalmic administration reduces risk. Use if potential benefit outweighs risk. |
| 3rd trimester | Considered safe for ophthalmic use near term; avoid systemic use near delivery due to theoretical risk of kernicterus. |
Clinical note
Comprehensive clinical and safety monograph for TOBREX (TOBREX).
| Placental transfer | Crosses placenta. Systemic absorption minimal after ophthalmic use; low levels in cord blood reported after intravenous administration. |
| Breastfeeding | Minimal systemic absorption after ophthalmic administration; unlikely to affect nursing infant. Use with caution due to theoretical risk of gut flora alteration or direct eye contact. |
■ 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 aminoglycosidesHistory of toxic reaction to aminoglycosides
| 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. |
| Food/Dietary | No significant food interactions. Avoid alcohol as it may reduce treatment compliance or exacerbate side effects. |
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| Lactation Rating | L2 (Safer) |
| 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. |
| 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. |
| Clinical Pearls |
| TOBREX (tobramycin ophthalmic solution/ointment) is an aminoglycoside antibiotic primarily used for ocular infections. Clinical pearls: 1) Avoid prolonged use to prevent microbial resistance and ocular toxicity. 2) Monitor for signs of hypersensitivity (e.g., lid itching, swelling). 3) Use with caution in patients with known aminoglycoside allergy. 4) In severe infections, consider combination therapy. 5) Do not touch dropper tip to any surface to avoid contamination. |
| Patient Advice | Wash hands before and after application. · Do not touch the dropper tip to your eye or any surface. · Use exactly as prescribed; do not skip doses or stop early. · May cause temporary blurred vision; avoid driving until clear. · Contact lens wearers should remove lenses before instillation and wait 15 minutes before reinsertion. · Report any signs of allergy such as itching, redness, or swelling. · Do not share this medication with others. · Finish the full course of therapy even if symptoms improve. |