Tobramycin (Bethkis, Tobi) — Compare Prices at US & Canada Pharmacies

Tobramycin is available in three quite different forms, and which one matters for a given patient depends entirely on what's being treated. As an IV or IM injection, it's used for serious systemic infections — sepsis, pneumonia, meningitis, complicated urinary tract and intra-abdominal infections — caused by susceptible Gram-negative bacteria including Pseudomonas aeruginosa, and this is where its boxed warning applies in full: real, well-documented nephrotoxicity and ototoxicity risk, with the auditory damage often irreversible and typically affecting both ears. As inhaled solution (Tobi, Bethkis) or dry powder (TOBI Podhaler), it's used cyclically to suppress chronic Pseudomonas infection in cystic fibrosis, delivering high local drug concentrations to the lungs while limiting systemic absorption and the toxicity that comes with it. As a 0.3% eye drop or ointment (Tobrex), it treats superficial bacterial eye infections with essentially no meaningful systemic exposure at all.

Because of this spread, the same drug carries very different real-world risk depending on the form: a patient on IV tobramycin for a serious infection needs kidney function and drug level monitoring that a patient using Tobrex eye drops for pink eye simply doesn't. The injectable formulation also contains sodium metabisulfite, a sulfite preservative that can trigger allergic-type or asthmatic reactions in sulfite-sensitive patients — a consideration specific to the injectable form, not the topical or inhaled ones.

Across all forms, cross-hypersensitivity with other aminoglycosides (gentamicin, amikacin, streptomycin, and others) is a recognized contraindication concern, and rare but serious skin reactions — including Stevens-Johnson syndrome and toxic epidermal necrolysis — have been reported with tobramycin therapy.

Boxed warning

WARNINGS Patients treated with Tobramycin Injection and other aminoglycosides should be under close clinical observation, because these drugs have an inherent potential for causing ototoxicity and nephrotoxicity. Neurotoxicity, manifested as both auditory and vestibular ototoxicity, can occur. The auditory changes are irreversible, are usually bilateral, and may be partial or total. Eighth-nerve impairment and nephrotoxicity may develop, primarily in patients having pre-existing renal damage and in those with normal renal function to whom aminoglycosides are administered for longer periods or in higher doses than those recommended.

Contraindications

CONTRAINDICATIONS A hypersensitivity to any aminoglycoside is a contraindication to the use of tobramycin. A history of hypersensitivity or serious toxic reactions to aminoglycosides may also contraindicate the use of any other aminoglycoside because of the known cross-sensitivity of patients to drugs in this class.

Warnings

WARNINGS See WARNINGS box above. This product contains sodium metabisulfite, a sulfite that may cause allergic-type reactions, including anaphylactic symptoms and life-threatening or less severe asthmatic episodes, in certain susceptible people. The overall prevalence of sulfite sensitivity in the general population is unknown and probably low. Sulfite sensitivity is seen more frequently in asthmatic than in non-asthmatic people. Serious allergic reactions including anaphylaxis and dermatologic reactions including exfoliative dermatitis, toxic epidermal necrolysis, erythema multiforme, and Stevens-Johnson Syndrome have been reported rarely in patients on tobramycin therapy.