What Is Tobramycin?

Tobramycin is an aminoglycoside antibiotic used to treat serious bacterial infections, including eye infections, Pseudomonas aeruginosa lung infections in cystic fibrosis patients, and systemic Gram-negative infections.

It's available under several brand names — Tobrex (eye drops), TOBI and TOBI Podhaler (inhaled forms), Bethkis, and Kitabis Pak — as well as in generic form. Tobramycin has been used since the 1970s and remains an important tool in fighting bacteria that are resistant to other antibiotics.

This guide covers everything you need to know about Tobramycin in 2026: what it treats, how it's taken, who should avoid it, and what it costs.

What Is Tobramycin Used For?

Tobramycin is FDA-approved for several conditions, depending on the formulation:

Eye Infections (Ophthalmic Drops and Ointment)

Tobramycin eye drops (0.3%) and ointment are used to treat bacterial conjunctivitis (pink eye), blepharitis, and other external eye infections caused by susceptible bacteria. They're one of the most commonly prescribed antibiotic eye drops and are approved for patients 2 months and older.

Cystic Fibrosis Lung Infections (Inhalation)

Inhaled Tobramycin — available as a nebulizer solution (300 mg/5 mL) or dry powder inhaler (TOBI Podhaler) — is used to manage chronic Pseudomonas aeruginosa lung infections in cystic fibrosis patients aged 6 and older. It's given in alternating 28-day on/off cycles to reduce lung bacterial load and improve breathing.

Serious Systemic Infections (Injection)

IV or IM Tobramycin is used for severe infections including:

• Septicemia (bloodstream infections)
• Lower respiratory tract infections
• Central nervous system infections (meningitis)
• Intra-abdominal infections
• Skin, bone, and soft tissue infections
• Complicated urinary tract infections

It's particularly effective against Gram-negative bacteria like Pseudomonas aeruginosa, E. coli, Klebsiella, and Enterobacter species.

Off-Label Uses

Doctors sometimes prescribe Tobramycin for conditions not on the official label, including empiric treatment of febrile neutropenia (in combination with beta-lactam antibiotics), peritonitis in peritoneal dialysis patients, and non-CF bronchiectasis with Pseudomonas colonization.

How Is Tobramycin Taken?

The dosage and method depend on which form you're using:

Eye Drops

• Mild to moderate infections: 1–2 drops in the affected eye every 4 hours
• Severe infections: 1–2 drops every hour until the infection improves, then reduce frequency
• Tilt your head back, pull down your lower eyelid, and place the drop in the pocket. Avoid touching the dropper tip to your eye or any surface.

Ophthalmic Ointment

• Apply a half-inch ribbon of ointment to the affected eye 2–3 times daily
• For severe infections, apply every 3–4 hours

Inhaled Tobramycin

• Nebulizer solution (TOBI, Bethkis, Kitabis Pak): 300 mg inhaled twice daily, doses should be about 12 hours apart (at least 6 hours apart)
• TOBI Podhaler: 4 capsules (112 mg total) inhaled twice daily
• Both are used in 28-day on/off cycles — 28 days of treatment, then 28 days off
• Take other CF medications first: bronchodilator, then dornase alfa, then Tobramycin

IV/IM Injection

• Standard dosing: 3–5 mg/kg/day divided into doses every 8 hours
• Once-daily (extended-interval) dosing: 5–7 mg/kg once daily — increasingly used in hospitals
• Administered in hospital or clinical settings with monitoring of blood levels and kidney function

Who Should Not Take Tobramycin?

Tobramycin is not appropriate for everyone. You should not use it if you have:

• Known allergy to Tobramycin or other aminoglycosides (such as Gentamicin or Amikacin) — there is cross-allergenicity between drugs in this class
• Myasthenia gravis — Tobramycin can worsen muscle weakness and potentially cause respiratory failure

Use with extreme caution if you have:

• Kidney impairment — dose adjustments and close monitoring are required
• Pre-existing hearing loss — risk of further damage is higher
• Pregnancy — IV/IM Tobramycin is Pregnancy Category D (evidence of fetal risk, including irreversible hearing loss in the baby)

Always tell your doctor about all medications you're taking. Tobramycin has significant drug interactions that can increase the risk of kidney damage and hearing loss.

How Much Does Tobramycin Cost?

The price of Tobramycin varies enormously depending on the formulation:

Generic Eye Drops (0.3%, 5 mL)

• Retail price: $5–$26
• With a coupon: As low as $4–$10
• This is one of the most affordable prescription eye drops available.

Injection (80 mg vial)

• Retail price: $5–$13
• With a coupon: As low as $4–$5

Inhaled Tobramycin (per 28-day cycle)

• Generic nebulizer solution: $2,500–$4,000+
• Brand TOBI: $8,000–$8,500+
• TOBI Podhaler: $8,000–$10,000+

For inhaled forms, insurance coverage and copay assistance are essential. Novartis offers the PODCARE+ Savings Card for TOBI Podhaler with up to $14,000 per year in copay assistance. Patient assistance programs are also available for uninsured or underinsured patients through the Novartis Patient Assistance Foundation.

For more ways to reduce your costs, see our guide on how to save money on Tobramycin.

Insurance Coverage

Generic Tobramycin eye drops are covered by most plans with low copays (Tier 1–2). Injectable Tobramycin is typically covered under your medical benefit when given in a clinical setting. Inhaled Tobramycin often requires prior authorization and may need documentation of a CF diagnosis with Pseudomonas culture results.

How Does Tobramycin Compare to Alternatives?

Several alternatives to Tobramycin exist, depending on the use case:

• Gentamicin — Another aminoglycoside, available as eye drops, injection, and topical cream. Generally less active against Pseudomonas than Tobramycin.
• Amikacin — A broader-spectrum aminoglycoside, often reserved for resistant infections. Retains activity against many Tobramycin-resistant bacteria.
• Moxifloxacin (Vigamox) — A fluoroquinolone eye drop alternative with broader Gram-positive coverage.
• Aztreonam (Cayston) — An alternative inhaled antibiotic for CF patients with Pseudomonas, also used in 28-day cycles.

Final Thoughts

Tobramycin is a versatile and effective antibiotic that has been a cornerstone of treatment for serious bacterial infections for decades. Whether you need it for a simple eye infection or as part of your cystic fibrosis care regimen, understanding how it works, how to take it, and what to watch for helps you get the most from your treatment.

If you're having trouble finding Tobramycin in stock or want to check pharmacy availability, Medfinder can help you locate it and compare prices near you.