dexamethasone + neomycin + polymyxin b sulfate: clinical use

Prescribing considerations

• Exclude viral, fungal, mycobacterial and untreated parasitic eye disease before prescribing.
• Assess for corneal or scleral thinning, dry eye, compromised corneal surface, diabetes and previous aminoglycoside hypersensitivity.
• Corticosteroids may mask infection, promote superinfection and delay corneal healing.
• Children may develop corticosteroid-induced ocular hypertension earlier than adults.
• Encourage nasolacrimal occlusion or gentle eyelid closure to reduce systemic absorption.

Contraindications and cautions

• Hypersensitivity to dexamethasone, neomycin, polymyxin B or an excipient
• Herpes simplex keratitis
• Vaccinia, varicella or another viral infection of the cornea or conjunctiva
• Fungal ocular disease or untreated parasitic eye infection
• Mycobacterial ocular infection

Monitoring

• Reassess worsening or persistent pain, redness, swelling or irritation.
• Monitor intraocular pressure during prolonged exposure, particularly in children and people predisposed to glaucoma or cataract.
• Evaluate persistent corneal ulceration for fungal infection and investigate new visual disturbance.
• Consider glucose monitoring in susceptible people and systemic corticosteroid surveillance when exposure is intensive, prolonged or combined with CYP3A4 inhibitors.

Clinical pharmacology

Dexamethasone is a synthetic glucocorticoid. Neomycin is an aminoglycoside that inhibits bacterial ribosomal protein synthesis; polymyxin B disrupts susceptible bacterial cytoplasmic membranes. Ocular administration generally produces low systemic exposure.

Formulation and product differences

• The eye drops are a suspension that must be shaken. They contain benzalkonium chloride, which may irritate dry or compromised eyes and can be absorbed by soft contact lenses.
• The ointment contains lanolin and parahydroxybenzoates, which may cause local or delayed allergic reactions.
• Ointment commonly causes temporary blurred vision and should be applied after other ophthalmic preparations.