Tobramycin

Key facts

• Tobramycin is an aminoglycoside antibiotic. As eye drops it treats bacterial conjunctivitis and other eye infections; given by injection or nebulizer, it treats serious infections, including lung infections in cystic fibrosis.
• Eye drops are used for short courses, usually up to a week or two, and stop once the infection has cleared.
• Given systemically, tobramycin can damage the kidneys and cause permanent hearing loss, ringing in the ears, or balance problems. Regular blood-level, kidney, and hearing checks are required during systemic treatment.
• Seek urgent care for ringing in the ears, hearing changes, dizziness, or a marked drop in urine output during systemic treatment.

What tobramycin treats

Tobramycin eye drops treat bacterial conjunctivitis and other surface eye infections caused by susceptible bacteria. Injectable tobramycin treats serious infections such as severe pneumonia, bloodstream infections, and infections caused by gram-negative bacteria that resist other antibiotics. Inhaled (nebulized) tobramycin is used long-term in people with cystic fibrosis to control chronic lung infections. Ear-drop formulations treat bacterial outer-ear infections.

How tobramycin works

Tobramycin enters bacterial cells and binds to their ribosomes, the machinery bacteria use to build proteins. This blocks the protein production the bacteria need to survive, and at the concentrations tobramycin reaches, it kills the bacteria outright rather than just slowing them.

Before you take it

• Tell your prescriber about any kidney problems, hearing loss, or balance disorders before starting systemic tobramycin. These raise the risk of further damage.
• Tell your prescriber about other medicines that can harm the kidneys or ears, such as certain diuretics, other aminoglycosides, and some other antibiotics; combining them increases risk.
• If you have had an allergic reaction to any aminoglycoside antibiotic, such as gentamicin or amikacin, tell your prescriber before using tobramycin in any form.
• Eye and ear drops should not be swallowed and are for the treated eye or ear only.

Side effects

Eye drops commonly cause mild stinging, redness, or temporary blurred vision. Systemic tobramycin commonly causes injection-site discomfort and can affect kidney function.

Stop and seek urgent medical care for any of these:

• Ringing in the ears, hearing loss, or a spinning sensation (vertigo), which can become permanent if treatment continues.
• Reduced urine output, swelling, or unusual tiredness, which can signal kidney injury.
• Signs of a severe allergic reaction: facial or throat swelling, rash, or difficulty breathing.

Safety essentials

• Systemic tobramycin can cause irreversible hearing or balance loss and kidney damage. Blood levels, kidney function, and hearing are monitored regularly during treatment to catch problems before they become permanent.
• Tell your care team immediately about any ringing in the ears, hearing changes, or dizziness. These can be early warning signs, and the drug may need to be stopped.
• Stay well hydrated during systemic treatment and avoid other kidney- or ear-damaging medicines unless your prescriber has confirmed it is safe.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.