BACITRACIN ZINC-NEOMYCIN SULFATE-POLYMYXIN B SULFATE
Clinical safety rating: safe
Animal studies have demonstrated safety
Bacitracin zinc inhibits bacterial cell wall synthesis by interfering with dephosphorylation of the lipid carrier that transports peptidoglycan precursors. Neomycin sulfate and polymyxin B sulfate are aminoglycoside and polypeptide antibiotics, respectively; neomycin binds to 30S ribosomal subunit and causes misreading of mRNA, while polymyxin B disrupts bacterial cell membrane permeability by interacting with phospholipids.
| Metabolism | Not systemically absorbed after topical administration; no significant metabolism. |
| Excretion | Neomycin: ~99% renal; polymyxin B: ~60% renal, 40% fecal; bacitracin: mainly renal (over 90%). Combined: renal (predominant), with minor biliary/fecal contribution (polymyxin B). |
| Half-life | Neomycin: 2-3 h; polymyxin B: 4.5-6 h; bacitracin: 1.5 h. Combined: effectively ~2-6 h depending on renal function; clinical context: prolonged with renal impairment. |
| Protein binding | Neomycin: 0-20%; polymyxin B: 60-80% (alpha-1-acid glycoprotein, albumin); bacitracin: <5%. Combined: ~40-50% bound overall. |
| Volume of Distribution | Neomycin: ~0.25 L/kg; polymyxin B: ~0.5 L/kg; bacitracin: ~0.3 L/kg. Combined Vd ~0.3-0.5 L/kg, reflecting limited distribution mainly to extracellular fluid. |
| Bioavailability | Topical/ophthalmic/otic: negligible systemic absorption (<0.1%). |
| Onset of Action | Topical: within 1-2 h; ophthalmic: 15-30 min; otic: 30-60 min. |
| Duration of Action | Topical: 6-8 h; ophthalmic: 4-6 h; duration sufficient for typical dosing intervals (3-4 times daily). |
Apply topically (ointment or cream) to affected area 1-3 times daily. For ophthalmic use, instill 1-2 drops into affected eye(s) every 3-4 hours.
| Dosage form | OINTMENT |
| Renal impairment | No systemic absorption with typical topical use; no adjustment necessary. For extensive use on damaged skin, monitor renal function and adjust if needed; no specific GFR-based guidelines. |
| Liver impairment | No adjustment needed for topical use. No systemic effects expected. |
| Pediatric use | Same as adult dosing for topical use. For neonates, use with caution on large surface areas; avoid prolonged use. |
| Geriatric use | No specific age-related adjustments. Use with caution on fragile skin; apply sparingly to avoid systemic absorption. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Other nephrotoxic or ototoxic drugs increase risk of toxicity Can cause ototoxicity and nephrotoxicity with systemic use.
| Breastfeeding | Minimal systemic absorption suggests negligible excretion into breast milk; M/P ratio not determined. Considered compatible with breastfeeding by AAP; avoid application to breast area to prevent infant ingestion. |
| Teratogenic Risk | No evidence of teratogenicity in first trimester; animal studies show no fetal harm. Second and third trimester risk is low due to minimal systemic absorption from topical use. No known association with congenital anomalies. |
■ FDA Black Box Warning
None.
| Common Effects | topical infections |
| Serious Effects |
["Hypersensitivity to any component of the product.","Otic use if tympanic membrane is perforated (risk of ototoxicity)."]
| Precautions | ["Prolonged use may result in overgrowth of nonsusceptible organisms including fungi.","Neomycin is ototoxic and nephrotoxic if absorbed systemically (e.g., applied to large areas of damaged skin).","Avoid contact with eyes other than for ophthalmic use.","Cross-allergenicity among aminoglycosides exists."] |
| Food/Dietary | No known food interactions with topical application. |
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| Fetal Monitoring |
| No specific monitoring required for topical use; if extensive skin breakdown or prolonged therapy, monitor for nephrotoxicity and ototoxicity (rare). |
| Fertility Effects | No known adverse effects on fertility based on available data; animal reproduction studies show no impairment. |
| Clinical Pearls | OTC triple antibiotic ointment; avoid use on deep wounds, puncture wounds, or animal bites due to risk of toxicity and lack of efficacy. Neomycin carries the highest risk of allergic contact dermatitis among topical antibiotics; consider patch testing if prolonged use needed. Polymyxin B can cause neurotoxicity and nephrotoxicity if applied to large wounds or damaged skin. Not for use in eyes, ears, or mucous membranes. Do not exceed 7 days of continuous use. |
| Patient Advice | Clean the affected area before applying a thin layer of ointment 1-3 times daily. · Do not use on large areas of skin, deep cuts, puncture wounds, or animal bites unless directed by a doctor. · Do not apply to eyes, nose, mouth, or inside ears. · Stop use and consult a doctor if rash or allergic reaction develops, condition worsens, or persists for more than 7 days. · Keep out of reach of children; seek medical attention if accidentally ingested. |