Dexamethasone / Tobramycin

Dexamethasone / tobramycin is a prescription combination used in the eye when both an anti-inflammatory steroid and antibiotic coverage are needed together. Supported uses across the available products include:

• Inflammatory conditions of the conjunctiva (the clear membrane covering the white of the eye) and cornea where a steroid is appropriate
• Inflammation of the anterior segment (front portion) of the eye
• Chronic anterior uveitis (ongoing inflammation inside the eye)
• Eye injury from chemical, radiation, or thermal burns, or penetration by a foreign body
• Situations where the risk of superficial bacterial eye infection is high, or where dangerous numbers of bacteria are likely present

Tobradex ST eye drops, Tobramycin and Dexamethasone eye drops, and TobraDex ointment all share these general indications. Product-specific details on dosing and formulation differ — see the form guidance section.

This combination works through two separate mechanisms. Dexamethasone is a potent corticosteroid — it suppresses the inflammatory response in the eye by reducing the activity of immune and inflammatory cells, which eases swelling, redness, and pain. Tobramycin is an aminoglycoside antibiotic that stops bacteria from making the proteins they need to survive, effectively halting their growth. Because the steroid alone can lower the eye's natural defenses and increase the risk of infection, tobramycin is included to help guard against susceptible bacteria.

In laboratory studies, tobramycin has also shown activity against some bacteria that are resistant to gentamicin, a related antibiotic — meaning it can cover a wider range of organisms in certain cases.

These products are applied directly to the eye — never swallowed or injected. Dosing frequency varies by product and by the severity of your condition at the start of treatment, so always follow your prescriber's exact instructions.

• Tobradex ST eye drops: typically one drop in the affected eye every 4 to 6 hours; may be increased to every 2 hours during the first 24–48 hours, then tapered as the eye improves. Shake well before use.
• Tobramycin and Dexamethasone eye drops: typically one or two drops every 4 to 6 hours; may be increased to every 2 hours in the first 24–48 hours.
• TobraDex ointment: a small ribbon (about half an inch) applied inside the lower eyelid up to three or four times daily.

Do not stop treatment early without talking to your doctor — incomplete treatment may allow inflammation or infection to return. Your doctor will re-evaluate you before authorizing a refill.

Side effects can come from either the antibiotic or the steroid component. The most common ones reported include:

• Eye pain
• Itching of the eyelids
• Eyelid swelling
• Eye redness (conjunctival hyperemia)
• Temporary blurred vision right after applying the medication
• Increased pressure inside the eye (intraocular pressure)
• Headache
• Increased blood pressure

More serious reactions to watch for include signs of rising eye pressure leading to glaucoma, cataract formation with prolonged use, a new or worsening eye infection, and allergic reactions ranging from local skin redness and itching to rare but serious whole-body reactions such as anaphylaxis. Contact your doctor or seek emergency help if you experience any of these.

• Increased eye pressure and glaucoma: Prolonged corticosteroid use can raise intraocular pressure, potentially damaging the optic nerve and causing vision loss. If you use this for 10 days or more, your doctor should check your eye pressure regularly.
• Cataract formation: Long-term steroid use in the eye can lead to a specific type of cataract (posterior subcapsular cataract) forming at the back of the eye's lens.
• Delayed healing and corneal risk: Steroids can slow healing after cataract surgery and, in people with conditions that thin the cornea or sclera, can even cause perforation (a hole forming in the eye wall).
• Masking or worsening infection: Steroids suppress immune defenses, which can hide a bacterial infection or allow it to worsen. If your eye is not improving after 2 days, see your doctor promptly.
• Viral and fungal infections: This medication must not be used for herpes-related or other viral eye infections, and fungal eye infections can develop or worsen with steroid use — especially with long-term use.
• Allergic reactions: Sensitivity to the aminoglycoside antibiotic (tobramycin) can range from local eye irritation to serious whole-body reactions. Stop use and seek care if this occurs.
• Contact lens use (Tobradex ST): Tobradex ST contains a preservative that soft contact lenses can absorb — do not wear soft lenses during treatment.

There are two key interaction concerns to be aware of with this medication:

• CYP3A4 inhibitors (examples include certain antifungal medications, some HIV drugs, and other medicines that block this liver enzyme) — these can increase the amount of dexamethasone that enters the bloodstream and may raise the risk of systemic steroid effects such as Cushing's syndrome (a condition from too much steroid exposure) or suppression of the adrenal glands, especially in children and those predisposed to these effects. Tell your doctor about all medications you take.
• Soft contact lenses — Tobradex ST eye drops contain benzalkonium chloride, a preservative that can be absorbed into soft contact lens material. Remove soft lenses before applying and ask your doctor or pharmacist when it is safe to reinsert them.

This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.

• Do not use if you have a viral eye infection — including herpes simplex keratitis (dendritic keratitis), chickenpox (varicella), or vaccinia involving the eye
• Do not use if you have a fungal or mycobacterial (such as tuberculosis-related) infection of the eye
• Tell your doctor if you have ever had herpes simplex eye disease — using a steroid in that setting requires great caution and close monitoring
• Tell your doctor about any allergy to tobramycin, dexamethasone, other aminoglycoside antibiotics, or any ingredient in these products
• Tell your doctor if you are pregnant or planning to become pregnant — corticosteroids have caused fetal harm in animal studies, and prolonged use during human pregnancy may be associated with reduced fetal growth; use only if clearly necessary
• Tell your doctor if you are breastfeeding — it is not fully known whether topical ophthalmic corticosteroids reach breast milk, so caution is advised
• Safety and effectiveness in children under 2 years old have not been established
• Tell your doctor if you have any condition that causes thinning of the cornea or sclera — the steroid component can increase the risk of a perforation
• Tell your doctor if you have or suspect neuromuscular disorders such as myasthenia gravis or Parkinson's disease — aminoglycosides may worsen muscle weakness

If too much of this medication is applied to the eye, signs can include punctate keratitis (small erosions on the cornea's surface), redness, increased tearing, eye swelling, and itchy eyelids — similar to some of the known side effects. Contact your doctor or poison control center if you are concerned about accidental overuse.

When applied to the eye, dexamethasone reaches the aqueous humor (the fluid inside the front of the eye) relatively quickly. After a single dose of Tobradex ST, concentrations in the aqueous humor peaked at an average of 33.7 ng/mL at about 2 hours. With regular use of tobramycin and dexamethasone ophthalmic suspension (four times a day for 2 days), peak levels of dexamethasone in the bloodstream were very low — less than 1 ng/mL — occurring within 2 hours after each dose, meaning systemic exposure is minimal. The extent to which tobramycin is absorbed into the bloodstream from Tobradex ST eye drops is not fully known.

Store upright at 20°-25°C (68°-77°F).