NEOMYCIN AND POLYMYXIN B SULFATES, BACITRACIN ZINC AND HYDROCORTISONE
Clinical safety rating: safe
Other nephrotoxic or ototoxic drugs increase risk of toxicity Can cause ototoxicity and nephrotoxicity with systemic use.
Neomycin, polymyxin B, and bacitracin are topical antibiotics that inhibit bacterial protein synthesis (neomycin and bacitracin) or disrupt bacterial cell membrane permeability (polymyxin B). Hydrocortisone is a corticosteroid that suppresses inflammation by inhibiting phospholipase A2, reducing prostaglandin and leukotriene synthesis.
| Metabolism | Topical application: minimal systemic absorption. If absorbed, neomycin is excreted unchanged in urine; polymyxin B is not significantly metabolized; bacitracin is excreted unchanged; hydrocortisone is metabolized in the liver via reduction and conjugation, excreted in urine. |
| Excretion | Neomycin is primarily excreted unchanged in feces (97%) after oral administration; absorbed fraction is renally excreted. Polymyxin B is mainly eliminated via renal tubular secretion (60-70% unchanged in urine). Bacitracin is predominantly excreted renally (90% unchanged). Hydrocortisone is metabolized hepatically and metabolites are excreted renally. For topical ophthalmic/otic use: negligible systemic absorption; any absorbed drug follows the respective systemic routes. |
| Half-life | Neomycin: 2-3 hours for absorbed fraction (extensive variability). Polymyxin B: 6-7 hours (prolonged in renal impairment). Bacitracin: 1.5 hours (intramuscular data; topical: negligible). Hydrocortisone: 1.5-2 hours (topical absorption limited). |
| Protein binding | Neomycin: 0-30% (minimal). Polymyxin B: ~80% (primarily to albumin). Bacitracin: minimal binding (data not well defined). Hydrocortisone: 90-95% (corticosteroid-binding globulin and albumin). |
| Volume of Distribution | Neomycin: 0.25 L/kg (absorbed fraction, limited). Polymyxin B: 0.5-1 L/kg (extensive tissue distribution). Bacitracin: 0.5-1 L/kg (intramuscular data). Hydrocortisone: 0.3-0.5 L/kg. These values are for systemic absorption; topical use yields negligible Vd. |
| Bioavailability | Oral: neomycin and polymyxin B <3% (neomycin), minimal for polymyxin B; bacitracin virtually none; hydrocortisone ~25% but negligible in this formulation. Ophthalmic/otic: negligible systemic absorption (<0.1% for most components). Topical: hydrocortisone bioavailability ~1-5% through intact skin. |
| Onset of Action | Topical ophthalmic/otic: relief of inflammation and infection within 24-48 hours; clinical effect may be noted as early as a few hours. Onset depends on infection severity. |
| Duration of Action | Ophthalmic/otic: apply 3-4 times daily per package insert; duration of therapy typically 7-10 days. Anti-inflammatory effect of hydrocortisone persists for hours; antimicrobial action continuous with repeated dosing. |
| Molecular Weight | Hydrocortisone: 362.46 Da; Neomycin sulfate: complex mixture, ~900 Da; Polymyxin B sulfate: ~1300 Da; Bacitracin zinc: ~1422 Da. |
Apply a thin layer to the affected area 2 to 4 times daily. Ophthalmic: 1-2 drops or a small amount (1/2 inch ribbon) into the conjunctival sac every 4 hours, or more frequently in severe infections. Otic: 4 drops into the affected ear(s) 3-4 times daily. Topical: Apply 2-4 times daily. Route: Topical, ophthalmic, otic.
| Dosage form | OINTMENT |
| Renal impairment | No adjustment necessary for topical use due to negligible systemic absorption. However, for extensive application on denuded skin or in patients with renal impairment, potential for systemic absorption; use with caution. Specific GFR-based adjustments are not established. |
| Liver impairment | No adjustment necessary for topical use. Not metabolized hepatically to a significant extent. |
| Pediatric use | Apply a thin layer to the affected area 2-4 times daily. For ophthalmic use, 1-2 drops or small amount every 4 hours. For otic use, 3-4 drops 3-4 times daily. Weight-based dosing not established; use same frequency as adults. |
| Geriatric use | No specific dose adjustments are recommended for elderly patients when used topically. Use with caution in patients with impaired renal function if applied to large areas of damaged skin. |
| 1st trimester | Limited human data; animal studies not available. Systemic absorption from topical application is minimal, but risk-benefit should be considered. Avoid use on large areas, broken skin, or under occlusive dressings. |
| 2nd trimester | Same as T1; systemic absorption minimal, but caution advised for prolonged use or high-dose application. |
| 3rd trimester | Same as T1; potential for fetal exposure is low with topical use, but avoid extensive use near term. |
Clinical note
Other nephrotoxic or ototoxic drugs increase risk of toxicity Can cause ototoxicity and nephrotoxicity with systemic use.
| FDA category | Animal |
| Placental transfer | Minimal to no placental transfer expected due to low systemic absorption after topical application. Bacitracin, neomycin, and polymyxin B are poorly absorbed through intact skin. |
■ FDA Black Box Warning
None.
| Common Effects | topical infections |
| Serious Effects |
Hypersensitivity to any componentPerforated tympanic membrane (otic use)Fungal or viral skin infections (e.g., herpes, varicella)Application to large areas of broken skin or open woundsConcurrent use with other ototoxic drugs (if applied to ear)
| Precautions | Prolonged use may lead to overgrowth of nonsusceptible organisms including fungi, Systemic absorption of neomycin may cause nephrotoxicity and ototoxicity, especially in patients with impaired renal function or prolonged use on large areas, Avoid use in eyes or for injection, May cause skin sensitization (type IV hypersensitivity to neomycin) |
| Food/Dietary | No significant food interactions. However, avoid excessive alcohol intake as it may worsen gastrointestinal side effects if systemic absorption occurs. |
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| Breastfeeding | Systemic absorption is negligible with topical use on intact skin, making significant transfer into breast milk unlikely. However, avoid application to the breast area to prevent infant ingestion. Use only on small areas and for short duration. |
| Lactation Rating | L2 (Safer) |
| Teratogenic Risk | Neomycin, polymyxin B, bacitracin, and hydrocortisone are poorly absorbed systemically when applied topically or ophthalmically. No well-controlled studies in pregnant women. Animal studies not available for combination; individual components: neomycin and polymyxin B not teratogenic in animals, bacitracin not teratogenic in rats, hydrocortisone is teratogenic in animals (cleft palate) after systemic administration. Systemic absorption of hydrocortisone from topical use is low but chronic high-dose use may cause fetal harm. Risk cannot be ruled out; use only if benefit outweighs risk. |
| Fetal Monitoring | No specific monitoring required for low systemic absorption. For prolonged use or large areas, monitor maternal adrenal suppression and fetal growth if hydrocortisone absorption suspected. |
| Fertility Effects | No known effects on fertility from topical use. Systemic effects not expected due to minimal absorption. |
| Clinical Pearls | Contains neomycin, polymyxin B, bacitracin (aminoglycoside + polypeptide antibiotics) and hydrocortisone (corticosteroid). Used for ophthalmic or otic infections with inflammation. Avoid prolonged use due to risk of secondary infections and corticosteroid-induced glaucoma/cataracts. Neomycin can cause contact sensitization; use with caution in patients with sulfite allergy (preservative). Systemic absorption from mucosal surfaces possible; avoid in perforated tympanic membrane (otic use) due to ototoxicity. |
| Patient Advice | Do not use for longer than prescribed; prolonged use can worsen infection or cause eye/ear damage. · Do not share this medication with others, even if they have similar symptoms. · Avoid touching the tip of the dropper or tube to any surface to prevent contamination. · For eye drops: wait at least 5 minutes between different eye medications. · Notify your doctor if you experience decreased vision, eye pain, or new symptoms after use. · If you have a perforated eardrum, do not use this in the ear unless directed by your doctor. · Inform your doctor if you are pregnant, planning to become pregnant, or breastfeeding. |