Adult: Available preparation
Polymyxin B 10,000 units/mL, neomycin 3,400 units/mL and hydrocortisone 10 mg/mL
Instill 3 drops into affected ear(s) 3-4 times daily. Alternatively, insert a gauze wick into the canal and keep it saturated with the solution for 24-48 hours. Discontinue if there is no clinical improvement after 7 days. Child: ≥3 years Same as adult dose.
Dosage reduction may be necessary.
Polymyxin B: Inactivated by strong acids and alkalis.
Hypersensitivity to polymyxin B, neomycin and hydrocortisone and other aminoglycosides. Perforated tympanic membrane, untreated viral, fungal and tubercular infections. Children <3 years.
Patient with conditions where significant systemic absorption may occur, venous stasis eczema and ulceration, pre- and post-operative period. Prolonged use. Children. Pregnancy and lactation.
Significant: Irreversible ototoxicity (e.g. deafness), nephrotoxicity, neurotoxicity, neomycin sensitisation (e.g. itching, reddening, oedema, failure to heal), immunosuppression, Kaposi sarcoma, and suppression of the pituitary-adrenal (HPA) axis after systemic absorption. Ear and labyrinth disorders: Stinging, burning sensation in ears. Potentially Fatal: Pseudomembranous colitis.
Neomycin and polymyxin may increase risk of respiratory depression with neuromuscular blocking agents.
Description: Polymyxin B is a bactericidal active against a wide range of gram negative bacilli. It binds to acid phospholipids in the bacterial cytoplasmic membrane, thereby altering permeability and disrupting the osmotic barrier leading to cell death.
Neomycin, an aminoglycoside, is a bactericidal active against a wide range of gram positive and gram negative bacteria. It interferes with bacterial protein synthesis by binding to 30S ribosomal subunits.
Hydrocortisone is a corticosteroid with both glucocorticoid and weak mineralocorticoid activity. It reduces inflammatory response by suppression of migration of polymorphonuclear leukocytes and reversal of increased capillary permeability. Pharmacokinetics: Absorption: Hydrocortisone: Absorbed through the skin particularly denuded areas. Distribution: Polymyxin B: Widely distributed and extensively bound to cell membranes in the tissues. Plasma protein binding: Approx 60%.
Neomycin: Distributed to tissues, concentrated in renal cortex.
Hydrocortisone: Crosses placenta. Plasma-protein binding: >90%. Metabolism: Hydrocortisone: Metabolised in the liver and tissues. Excretion: Polymyxin B: Via urine. Elimination half-life: Approx 6 hour.
Neomycin: Via urine. Elimination half-life: 2-3 hour.
Hydrocortisone: Mainly via urine (mostly as conjugated glucuronide), with small amounts as unchanged drug. Plasma elimination half-life: Approx 100 minutes.