Usage
Dexamethasone + Neomycin is a combination medication primarily used to treat bacterial infections of the eye accompanied by inflammation. It is commonly prescribed for conditions such as blepharitis, conjunctivitis, and keratitis. It is also used after eye surgery and for eye injuries, radiation, or chemical burns.
Its pharmacological classifications are:
- Antibiotic: Neomycin (aminoglycoside) and Polymyxin B (polymyxin)
- Corticosteroid: Dexamethasone
Mechanism of Action: Neomycin and Polymyxin B exert bactericidal effects by inhibiting bacterial protein synthesis and increasing bacterial cell membrane permeability, respectively. Dexamethasone, a corticosteroid, provides anti-inflammatory and immunosuppressive action by modulating inflammatory mediators.
Alternate Names
Dexamethasone + Neomycin + Polymyxin B. Brand names include Maxitrol, Poly-Dex, Ocu-Trol, Dexacidin, Dexasporin, Methadex, AK-Trol, and Dexacine.
How It Works
Pharmacodynamics: Neomycin and Polymyxin B work synergistically to kill a broad spectrum of bacteria commonly causing eye infections. Dexamethasone suppresses the inflammatory cascade, reducing redness, swelling, pain, and itching.
Pharmacokinetics: The ophthalmic formulation primarily provides local action in the eye. Systemic absorption is minimal, minimizing systemic side effects. The small amounts that are systemically absorbed are metabolized by the liver and excreted by the kidneys.
Mode of Action: Neomycin binds to bacterial ribosomes, disrupting protein synthesis. Polymyxin B interacts with the bacterial cell membrane, leading to leakage and cell death. Dexamethasone interacts with intracellular glucocorticoid receptors to alter gene expression, ultimately inhibiting inflammatory mediators.
Elimination: Primarily through renal excretion for neomycin. Hepatic metabolism and renal excretion for dexamethasone. Polymyxin B is primarily renal excretion.
Dosage
Standard Dosage
Adults: 1-2 drops into the affected eye(s) every 4-6 hours. Frequency can be increased to hourly in severe infections, followed by tapering as inflammation subsides. Ointment: Apply a small ribbon (approximately 1/2 inch) into the conjunctival sac(s) 1–4 times a day.
Children: The safety and effectiveness of this ophthalmic preparation have not been established in children below two years of age. For children 2 years and older, follow adult dosing.
Special Cases:
- Elderly Patients: Use with caution; close monitoring for adverse effects, especially increased intraocular pressure, is recommended.
- Patients with Renal Impairment: No dose adjustment is typically necessary due to minimal systemic absorption.
- Patients with Hepatic Dysfunction: No dose adjustment is typically necessary due to minimal systemic absorption.
- Patients with Comorbid Conditions: Use with caution in patients with glaucoma, diabetes, or history of herpes simplex keratitis.
Clinical Use Cases
Dosing follows standard recommendations. The frequency may be increased based on the severity of inflammation and infection.
Dosage Adjustments
Dosage is primarily adjusted based on the severity of the infection and inflammation. Close monitoring of intraocular pressure is important, especially in patients with glaucoma or risk factors for glaucoma.
Side Effects
Common Side Effects
Blurred vision, mild eye irritation, burning or stinging, itching, redness, eyelid itching, and photosensitivity.
Rare but Serious Side Effects
Allergic reactions (hives, difficulty breathing, swelling), signs of secondary infection (increased redness, pain, discharge), glaucoma, vision changes, and delayed wound healing.
Long-Term Effects
Cataracts, glaucoma, thinning of the cornea or sclera, and optic nerve damage with prolonged use.
Adverse Drug Reactions (ADR)
Severe allergic reactions, significant increases in intraocular pressure, and secondary infections (especially fungal).
Contraindications
Hypersensitivity to any component of the medication. Viral infections of the cornea and conjunctiva (herpes simplex, vaccinia, varicella). Mycobacterial, fungal, or untreated parasitic eye infections.
Drug Interactions
No significant drug interactions have been reported with ophthalmic use. Always inform your doctor about all other medications, including over-the-counter drugs and supplements, that the patient is taking.
Pregnancy and Breastfeeding
Pregnancy: Not recommended. Potential risks to the fetus exist. Use only if clearly needed and the potential benefit outweighs the risk.
Breastfeeding: Caution advised. Systemically administered corticosteroids appear in human milk and could cause side effects in the infant. While topical ophthalmic application results in minimal systemic absorption, it is unknown whether this would be sufficient to cause detectable quantities in human milk. It is advised to weigh the potential benefits against the potential risks.
Drug Profile Summary
- Mechanism of Action: Antibiotic and anti-inflammatory.
- Side Effects: Eye irritation, blurred vision, allergic reactions.
- Contraindications: Hypersensitivity, viral/fungal eye infections.
- Drug Interactions: None significant reported with ophthalmic use.
- Pregnancy & Breastfeeding: Not recommended during pregnancy. Caution during breastfeeding.
- Dosage: See Dosage section above.
- Monitoring Parameters: Intraocular pressure, signs of infection, allergic reactions.
Popular Combinations
This medication is typically used as a standalone treatment for ocular infections and inflammation.
Precautions
Assess for allergies, glaucoma, and herpes simplex history. Monitor for secondary infections. Advise patients about proper administration techniques to avoid contamination. Caution in pregnancy and breastfeeding.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Dexamethasone + Neomycin ophthalmic?
A: For adults and children over 2 years, 1-2 drops in the affected eye(s) every 4-6 hours, or more frequently in severe cases. Ointment can be applied 1–4 times a day.
A: Contact lenses should be removed before instillation and may be reinserted 15-20 minutes after administration. However, prolonged use of this medication is not recommended while wearing contact lenses.
Q3: What should I do if I miss a dose?
A: Instill the missed dose as soon as remembered. If it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule.
Q4: Can this medication be used for viral eye infections?
A: No. This medication is contraindicated in viral eye infections and can exacerbate certain viral infections, such as herpes simplex keratitis.
Q5: Are there any long-term risks associated with the use of this medication?
A: Yes. Prolonged use can increase the risk of glaucoma, cataracts, thinning of the cornea and sclera, and optic nerve damage.
Q6: What are the signs of an allergic reaction to this medication?
A: Itching, redness, swelling of the eyelids, hives, difficulty breathing, and swelling of the face, lips, tongue, or throat. Seek immediate medical attention if these occur.
Q7: Can I use this medication while pregnant or breastfeeding?
A: It is generally not recommended during pregnancy due to potential risks to the fetus. Caution should be exercised during breastfeeding, and the decision to use it should be made in consultation with a physician, weighing the potential benefits against the risks.
Q8: How long should I use this medication?
A: Use it for the prescribed duration, even if symptoms improve. Do not stop using it prematurely without consulting the physician.
Q9: Can I drive after using this medication?
A: This medication may temporarily blur vision. Avoid driving or operating machinery until vision clears.
