Tobramycin, or Tobrex, is a type of antibiotic eye drop. Specifically, it is an aminoglycoside that kills specific bacteria by blocking the protein synthesis that they cause. As a result, they cannot create functional proteins and they start to die off. It should be noted, however, that Tobramycin eye drops work only for bacterial eye infections, not viral ones.

What Are Tobramycin Eye Drops?

The U.S. Food and Drug Administration approved Tobramycin in December 1980. It is available both in a drop formulation and as a 0.3% ointment. The ointment is offered to those whose bacterial infection is on the outside of the eye.

Tobramycin is a prescription only drug that is now generically available. It should be stored at room temperature at all times.

How to Use Tobramycin

It is very important to follow the exact instructions of a physician when using Tobramycin. For those over two months of age, one to two drops should be placed in the affected eye every four to six hours. If the infection is severe, drops should be placed every half hour to an hour until there is an improvement, after which the dosing intervals can be lengthened.

Before applying Tobramycin, remember to:

• Thoroughly wash your hands before and after using the drops.
• Not wear contact lenses while the infection is present.
• Dispose of contact lenses worn while the infection was present.
• Not touch the eye with the dropper tip.
• Wait at least five minutes between different eye drops.

It is important not to use Tobramycin if you have known allergies to any of the ingredients. Additionally, before taking it, you should tell your physician if you are:

• Trying to conceive, pregnant, or nursing a baby.
• Taking any medication, prescription, over the counter, herbal, or supplemental.
• Allergic to any substance, even those not found in Tobramycin.

To apply the drops, follow seven steps:

1. Tilt the head back.
2. Pull your lower eyelid with your index finger so that it forms a pouch away from the eye.
3. Drop the medicine in the pouch.
4. Close the eye.
5. Put pressure on the corner of the eyelid immediately for one or two minutes.
6. Do not blink.
7. Use a clean tissue to remove excess drops.

It is very important to complete the full course as prescribed by your physician. Do also try to use the drops at the same time every day, and do not miss your dose. If you do miss one dose, use it as soon as possible, unless it is very close to the time of your next dose.

Tobramycin Side Effects

Some of the most commonly reported side effects of Tobramycin are:

• Swelling of the eye
• Tearing
• Burning, stinging, and itching of the eye
• Blurred vision after administration

If you experience any of these side effects, you may not engage in activities, such as driving, until you notice an improvement.

It is rare for someone to suffer an allergic reaction to Tobramycin. However, in the rare occasions that it does happen, medical attention must be sought immediately. Possible indications of an allergic reaction include:

• Swelling of the tongue, throat, or face
• Difficulty breathing
• Severe rash

Drug Interactions and Other Concerns

There are very few known drug interactions with Tobramycin. This is mainly due to the drops not becoming clinically measurable in the blood. However, it is important to receive confirmation from a physician before applying the drug together with any other eye drops, including over the counter ones. There are some medicines that are believed to possibly interact with Tobramycin. This is why it is very important to speak to a physician and tell them if:

• You have cephalosporin injections such as ceftazidime, as this can decrease the effectiveness of the drops.
• You currently take vancomycin injections; polypeptide antibiotics like polymyxin B; nitrosoureas like streptozocin; nonsteroidal anti-inflammatory drugs (NSAIDs) like indomethacin and methoxyflurane; or loop diuretics like furosemide, fludarabine, and cyclosporine. All of these drugs can put you at an increased risk of developing side effects with Tobramycin. Hearing and kidney problems have been most commonly reported.
• If you currently take succinylcholine or nondepolarizing muscle relaxants like pancuronium, as their side effects can be increased when using Tobramycin.

Because the drug does not become clinically measurable in the blood, it can also be used during pregnancy. According to the U.S. Food and Drug Administration, it is a category B risk (which means no harm to fetus or fertility has been found in animal testing with the drug). However, there have been no proper tests on how the drug affects human pregnancies directly. Hence, it is only prescribed to pregnant mothers if it is truly needed.

For nursing mothers, low concentration of aminoglycoside antibiotics can be found in breast milk. The risk of this negatively affecting the baby is unknown. However, a physician will need to determine whether the benefits of the drug outweigh the low risk of exposing an infant to the drug.

Final General Information

A few final things to be aware of with Tobramycin:

1. Always speak to your health care provider, pharmacist, doctor, or ophthalmologist if you have any questions about the product.
2. Never share your medication with others. It is a prescription drug and should therefore only be used by you.
3. Get in touch with your physician if there is no improvement in your symptoms after a few days, or if they get worse at any time.
4. Dispose of any unused medication properly. Speak to your physician if you are unsure of the proper procedures in your area.

Resources and References:

Tobrex – Information on tobramycin ophthalmic solution (MedicineNet.com)

Drugs@FDA – U.S. Food and Drug Administration Tobramycin Approval (FDA.gov)