TOBRADEX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TOBRADEX (TOBRADEX).
Tobradex is a combination of tobramycin (an aminoglycoside antibiotic) and dexamethasone (a corticosteroid). Tobramycin inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit, causing misreading of mRNA and cell death. Dexamethasone suppresses inflammation by inhibiting phospholipase A2, reducing prostaglandin and leukotriene synthesis, and decreasing cytokine production.
| Metabolism | Tobramycin is not metabolized; primarily excreted unchanged in urine. Dexamethasone is metabolized in the liver via CYP3A4 to inactive metabolites. |
| Excretion | Tobramycin: ~90% renal (glomerular filtration), <1% biliary. Dexamethasone: hepatic metabolism, metabolites renally excreted. |
| Half-life | Tobramycin: 2-3 hours in adults with normal renal function; prolonged to 24-60 hours in anuria. Dexamethasone: 36-54 hours. |
| Protein binding | Tobramycin: <10% bound to plasma proteins. Dexamethasone: ~77% bound, primarily to albumin. |
| Volume of Distribution | Tobramycin: 0.26 L/kg (extracellular fluid compartment). Dexamethasone: 0.75-1.3 L/kg. |
| Bioavailability | Ophthalmic: limited systemic absorption via cornea; approximately 50% of topically applied tobramycin is absorbed through the cornea, but systemic bioavailability is very low due to drainage and dilution. |
| Onset of Action | Ophthalmic: antibacterial effect within hours after topical application; anti-inflammatory effect within 24 hours. |
| Duration of Action | Ophthalmic: dosing every 4-6 hours for anti-inflammatory effect; antibacterial duration depends on concentration above MIC. |
1-2 drops into the affected eye(s) every 4-6 hours; in severe disease, every 1-2 hours initially, then taper. Ointment: apply a 1/2-inch ribbon into the conjunctival sac 3-4 times daily.
| Dosage form | OINTMENT |
| Renal impairment | No adjustment required for ophthalmic use. |
| Liver impairment | No adjustment required for ophthalmic use. |
| Pediatric use | Same as adult dosing for children ≥2 years; use dose per weight not established, clinical judgment advised. |
| Geriatric use | No specific adjustment; use with caution due to increased risk of intraocular pressure elevation and infection. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TOBRADEX (TOBRADEX).
| Breastfeeding | Minimal systemic absorption after topical ophthalmic use; no M/P ratio available. Considered compatible with breastfeeding; caution with prolonged use. |
| Teratogenic Risk | Corticosteroids are associated with increased risk of cleft palate (first trimester) and fetal adrenal insufficiency (chronic use). Tobramycin is an aminoglycoside; risk of ototoxicity and nephrotoxicity is theoretical but not confirmed at typical ophthalmic doses. Avoid systemic exposure; topical ophthalmic use has minimal systemic absorption, but risk cannot be completely excluded. |
■ FDA Black Box Warning
Not applicable; no FDA black box warning exists for Tobradex.
| Serious Effects |
["Hypersensitivity to tobramycin, dexamethasone, or any component","Active viral infections (e.g., herpes simplex keratitis)","Fungal infections of the eye","Uncontrolled ocular hypertension","Mycobacterial infections"]
| Precautions | ["Prolonged use may lead to ocular hypertension/glaucoma","Secondary ocular infections (fungal, viral) may develop","Corneal perforation risk in patients with corneal thinning","Systemic absorption may occur with prolonged use","Not for use in fungal or viral infections of the eye"] |
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| Fetal Monitoring |
| No specific monitoring required for topical ophthalmic use. If used long-term or in high doses, consider fetal ultrasound for growth and adrenal function. |
| Fertility Effects | No known effects on fertility from topical ophthalmic use. |