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Tobramycin (ophthalmic/eye antibiotic)

Written by Stephanie Nera, RPh, PharmD · Pharmacology

Updated Jun 23, 2021

Tobramycin is part of a class of antibiotics known as aminoglycosides. Aminoglycosides work by binding to the 30S and 50S subunits of bacterial ribosomes. This binding interferes with bacterial protein synthesis, resulting in reduced growth, defective bacterial cell membrane, and eventual bacterial cell death.

Aminoglycosides have the same mechanism as penicillin, however, have enhanced resistance against β-lactamases.



What is tobramycin used for?

Tobramycin is a broad-spectrum antibiotic mainly indicated for:

  • Susceptible infections
  • Mild-to-moderate urinary tract infections (UTIs)
  • Cystic fibrosis
  • Ocular infections

How should I take tobramycin?

Tobramycin is commercially available as an ophthalmic (eye) drop and ointment preparations. The eye drops should be instilled into the affected eye(s) as directed. Do not touch the tip of the dropper with your finger or eye. For the ointment, apply a ribbon of ointment direction onto the affected eye(s) as directed.

Parenteral and inhalational dosage forms are used for certain conditions, however, are not commonly used.

How do I store tobramycin?

This product is best stored at controlled room temperature away from direct light and moisture. To prevent drug damage, you should not store it in the bathroom or the freezer. 

There may be different brands of this drug that may have different storage needs. So, it is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush this product down the toilet or pour them into a drain unless instructed to do so. Additionally, it is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Precautions & warnings

What should I know before using tobramycin?

Before using this drug, tell your doctor if you are/have:

  • Pregnant or breastfeeding.
  • Taking any other medicines. This includes any prescription, OTC, and herbal remedies.
  • An allergy to any of the ingredients of this product.
  • Any other illnesses, disorders, or medical conditions.

Is it safe during pregnancy or breastfeeding?

Tobramycin is a pregnancy category B drug in the ophthalmic preparation form and category D in parenteral and inhalational dosage forms. There are no adequate and well-controlled studies using tobramycin in pregnant women. It should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus, as determined by your doctor.

This drug may be excreted in breast milk. It drug should be used while breastfeeding only if the potential benefit justifies the potential risk to the child, as determined by your doctor.

Side effects

What side effects can occur when using tobramycin?

Like all drugs, this product may have side effects. If they occur, side effects are generally mild and resolve once treatment is finished or the dose is lowered. Some reported side effects include:

  • Localized ocular toxicity
  • Conjunctival erythema (redness)
  • Punctate keratitis
  • Increased lacrimation (tear production)

Rare, serious adverse reactions:

  • Neurotoxicity
  • Nephrotoxicity
  • Anaphylactic reaction
  • Exfoliative dermatitis
  • Toxic epidermal necrolysis (TEN)
  • Stevens-Johnson syndrome (SJS)
  • Erythema multiforme
  • Neuromuscular blockage or respiratory paralysis

However, not everyone experiences these side effects. In addition, some people may experience other side effects. So, if you have any concerns about a side effect, please consult your doctor or pharmacist.


What drugs may interact with tobramycin?

This medication may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. 

To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs, and herbal products) and share it with your doctor and pharmacist. 

Drugs with known interactions:

  • Allopurinol
  • Amphotericin B cholesteryl sulfate complex
  • Azithromycin
  • Heparin
  • Hetastarch in NS
  • Indomethacin
  • Pantoprazole
  • Pemetrexed
  • Piperacillin (with or without tazobactam)
  • Propofol
  • Sargramostim

If you experience an adverse drug interaction, inform your doctor immediately to reevaluate your treatment plan. Approaches include dose adjustment, drug substitution, or ending therapy.

Does food or alcohol interact with tobramycin?

This drug may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

What health conditions may interact with tobramycin?

This drug may interact with underlying conditions. This interaction may worsen your health condition or alter the way the drug works. Therefore, it is important to always let your doctor and pharmacist know all the health conditions you currently have, especially:

  • History of hypersensitivity to aminoglycosides
  • Neuromuscular disorders
  • Renal impairment


The information provided is not a substitute for any medical advice. Therefore, you should always consult with your doctor or pharmacist before using any medication.

What is the dose for an adult?

Ocular (eye) infections

  • As 0.3% eye drops: instill 1 drop into the conjunctival sac once in the morning and evening.
    • For severe infections, instill 4 times on the first day, then two times a day for the succeeding days.
  • As 0.3% ointment: apply a half-inch ribbon into the affected eye(s) 2 to 3 times per day.
    • For severe infections, apply every 3 to 4 hours

What is the dose for a child?

Ocular (eye) infections

  • For ages >1 year: Same as the adult dose.
  • <1 year: Do not give this medication.

How is tobramycin available?

This drug is available in the following brands, dosage forms, and strengths:

  • Celsus eye drops 0.3% (3 mg/mL)
  • Sensomed eye drops 0.3% (3 mg/mL)
  • Tobrex eye drops 3 mg/mL
  • Tobrex eye ointment 3 mg/g
  • Tomracin eye drops 3 mg/mL

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to the nearest emergency room.

What should I do if I miss a dose?

If you miss a dose, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.


Hello Health Group does not provide medical advice, diagnosis or treatment.

Written by

Stephanie Nera, RPh, PharmD


Updated Jun 23, 2021

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