What it's for (Indications)
- This ophthalmic combination preparation, containing dexamethasone, tobramycin, and polymyxin B, is indicated for the treatment of superficial bacterial infections of the eye and its adnexa where corticosteroid action is also desired to reduce inflammation.
- Specific indications include bacterial conjunctivitis, blepharitis, keratitis, dacryocystitis, and post-operative inflammation with an associated risk of bacterial infection.
- It is particularly useful in conditions where the inflammatory component is significant and the causative organisms are susceptible to tobramycin and polymyxin B.
- This combination addresses both the infectious etiology and the inflammatory response, aiming to mitigate tissue damage and discomfort while eradicating susceptible bacteria.
- It is crucial to obtain appropriate microbiological samples before initiating therapy to confirm the bacterial susceptibility and rule out non-bacterial etiologies, although empiric treatment may be warranted in urgent clinical situations after careful assessment of the clinical presentation and risk factors.
- This therapeutic approach is intended for short-term use to manage acute inflammatory and infectious episodes.
Dosage Information
| Type | Guideline |
|---|---|
| Standard | For ophthalmic solution, the typical dosage involves instilling one or two drops into the conjunctival sac of the affected eye(s) every four to six hours. During the initial 24 to 48 hours, the dosage may be increased to one or two drops every two hours, based on the severity of the infection and inflammation, under strict medical supervision and careful monitoring. For ophthalmic ointment, a small amount (approximately a 1/2-inch ribbon) should be applied into the conjunctival sac of the affected eye(s) three to four times a day, or as a bedtime dose when used in conjunction with the solution. Treatment duration should generally not exceed 7 to 10 days to minimize the risk of corticosteroid-induced adverse effects such as elevated intraocular pressure and secondary infections. Prolonged use requires careful and frequent monitoring by an ophthalmologist, including regular intraocular pressure measurements and slit-lamp examinations. Patients should be advised not to discontinue treatment prematurely, even if symptoms improve, to ensure complete eradication of the infection and prevent recurrence or development of antibiotic resistance. |
Safety & Warnings
Common Side Effects
- Ocular side effects are the most commonly reported with this ophthalmic combination.
- These include transient stinging, burning, itching, foreign body sensation, and redness upon instillation.
- Prolonged use of the corticosteroid component, dexamethasone, can lead to increased intraocular pressure (IOP) and potentially glaucoma, with damage to the optic nerve, visual field defects, and posterior subcapsular cataract formation.
- Corneal thinning may occur, and in conditions that cause thinning of the cornea or sclera, perforations may develop, especially with extended use.
- Secondary ocular infections, particularly fungal or viral (e.
- g.
- , herpes simplex), are a significant risk with corticosteroid use, as they can mask or exacerbate existing infections.
- Allergic reactions, including eyelid edema, conjunctival erythema, and itching, may occur due to any of the components, necessitating discontinuation.
- Although rare with topical ophthalmic administration, systemic absorption could theoretically lead to aminoglycoside-related ototoxicity or nephrotoxicity, especially with compromised ocular barriers or prolonged, high-dose use; however, this is exceedingly uncommon and typically associated with systemic administration of aminoglycosides.
- Other less common side effects include blurred vision and sensitivity to light.
Serious Warnings
- Black Box Warning: This ophthalmic combination does not carry a formal FDA Black Box Warning. However, several serious warnings merit explicit attention due to the active components. **Serious Ocular Hypertension and Glaucoma:** Prolonged use (typically exceeding 10 days) of the corticosteroid component, dexamethasone, can lead to a significant increase in intraocular pressure (IOP) and the development of glaucoma, potentially causing optic nerve damage, visual field defects, and irreversible vision loss. Patients, especially those with a history of glaucoma, should be carefully monitored with regular IOP measurements. **Cataract Formation:** Long-term corticosteroid use is also associated with the formation of posterior subcapsular cataracts. **Secondary Ocular Infections:** The use of corticosteroids can suppress the host immune response, thereby increasing the risk of secondary ocular infections from fungi, viruses (including herpes simplex), or other opportunistic pathogens. In acute purulent infections, corticosteroids may mask infection or enhance its spread, requiring careful diagnostic evaluation. **Corneal Perforation:** In diseases causing thinning of the cornea or sclera, topical corticosteroids can lead to perforation. **Aminoglycoside Hypersensitivity:** Sensitization to topical aminoglycosides like tobramycin can occur, manifesting as lid itching, swelling, and conjunctival erythema, potentially requiring discontinuation. Cross-sensitivity to other aminoglycosides is possible. **Overgrowth of Non-Susceptible Organisms:** As with other antibiotics, prolonged use of tobramycin and polymyxin B may result in the overgrowth of non-susceptible bacteria or fungi, necessitating re-evaluation and alternative therapy. Strict adherence to dosage and duration limits is crucial to mitigate these risks.
- Prolonged use of corticosteroids in the eye, including dexamethasone, may result in increased intraocular pressure (IOP) and glaucoma, with potential damage to the optic nerve, defects in visual acuity and fields of vision, and posterior subcapsular cataract formation.
- Regular monitoring of IOP is imperative for patients receiving prolonged corticosteroid therapy (e.
- g.
- , beyond 10 days) or those with a history of glaucoma.
- The possibility of persistent fungal infections of the cornea should be considered in any persistent corneal ulceration where a corticosteroid has been used or is in use, as corticosteroids can promote the growth of fungi.
- Acute purulent untreated infections of the eye may be masked or enhanced by the presence of corticosteroid medication.
- In those diseases causing thinning of the cornea or sclera, perforations have been known to occur with the use of topical steroids.
- Sensitization to topically applied aminoglycosides, including tobramycin, may occur in some patients, potentially leading to allergic reactions such as lid itching, swelling, and conjunctival erythema; cross-sensitivity to other aminoglycosides can also occur.
- The prolonged use of antibiotics may result in the overgrowth of non-susceptible organisms, including fungi, necessitating appropriate re-evaluation and alternative therapy.
- Patients should be advised against wearing contact lenses during treatment for ocular infections to prevent further irritation or complications.
How it Works (Mechanism of Action)
The therapeutic efficacy of this ophthalmic combination stems from the synergistic actions of its three active components. **Dexamethasone** is a potent synthetic corticosteroid that exerts its anti-inflammatory and immunosuppressive effects by diffusing across cell membranes and binding to specific cytoplasmic receptors. This complex then translocates into the nucleus, binding to DNA and altering gene expression, leading to the synthesis of inhibitory proteins (e.g., lipocortins) that suppress the release of inflammatory mediators like prostaglandins and leukotrienes. It also reduces capillary permeability and suppresses polymorphonuclear leukocyte migration, thereby diminishing the inflammatory response, pain, and swelling. **Tobramycin** is an aminoglycoside antibiotic that acts by irreversibly binding to the 30S ribosomal subunit of susceptible bacteria. This binding interferes with bacterial protein synthesis, leading to misreading of the mRNA code and incorporation of incorrect amino acids into growing peptide chains, ultimately resulting in the production of non-functional proteins and bacterial cell death (bactericidal action). **Polymyxin B** is a polypeptide antibiotic that primarily targets the outer membrane of Gram-negative bacteria, such as *Pseudomonas aeruginosa*. It acts as a cationic detergent, interacting with the anionic lipopolysaccharide component of the bacterial outer membrane, which disrupts membrane integrity and increases permeability. This leads to leakage of intracellular components and rapid bacterial cell death, demonstrating a bactericidal effect. The combination provides broad-spectrum antibacterial coverage alongside potent anti-inflammatory relief to manage complex ocular infections effectively.
Commercial Brands (Alternatives)
No other brands found for this formula.