BACITRACIN ZINC-POLYMYXIN B SULFATE
Clinical safety rating: safe
No significant systemic drug interactions due to minimal absorption For topical use only not for eyes or deep wounds.
Bacitracin zinc inhibits bacterial cell wall synthesis by binding to undecaprenyl pyrophosphate and blocking peptidoglycan synthesis. Polymyxin B sulfate disrupts bacterial cell membrane integrity by binding to lipopolysaccharides and phospholipids, increasing permeability leading to cell death.
| Metabolism | Not systemically absorbed following topical application; if absorbed, bacitracin is excreted renally unchanged and polymyxin B undergoes renal elimination. |
| Excretion | Renal: minimal (mainly unabsorbed drug excreted in feces after oral administration; for topical use, negligible systemic absorption) |
| Half-life | Not applicable due to negligible systemic absorption; if absorbed, renal elimination half-life unknown |
| Protein binding | Not characterized due to minimal systemic availability; expected low if absorbed |
| Volume of Distribution | Not applicable due to minimal systemic absorption; theoretical if absorbed: likely <0.3 L/kg |
| Bioavailability | Topical/ophthalmic: negligible (<1% systemic absorption); oral: not absorbed |
| Onset of Action | Topical: within 24–48 hours for reduction of bacterial counts; ophthalmic: within 1–2 hours |
| Duration of Action | Topical: 6–8 hours between applications; ophthalmic: up to 4–6 hours |
| Molecular Weight | Bacitracin: ~1422 Da; Polymyxin B: ~1303 Da |
Apply to affected area 2 to 3 times daily; not for injection or ophthalmic use.
| Dosage form | OINTMENT |
| Renal impairment | No systemic absorption with topical use; no adjustment required. |
| Liver impairment | No systemic absorption with topical use; no adjustment required. |
| Pediatric use | Same as adult dosing: apply to affected area 2 to 3 times daily. |
| Geriatric use | Same as adult dosing; no specific adjustments needed. |
| 1st trimester | Topical use is generally considered safe due to minimal systemic absorption. Systemic use should be avoided due to potential nephrotoxicity and ototoxicity. |
| 2nd trimester | Same as T1. Topical use is considered low risk; systemic administration is contraindicated due to adverse effects. |
| 3rd trimester | Same as T1 and T2. Avoid systemic use near term due to risk of neonatal toxicity. |
Clinical note
No significant systemic drug interactions due to minimal absorption For topical use only not for eyes or deep wounds.
| FDA category | Animal |
| Placental transfer | Bacitracin: limited data, but due to high molecular weight, minimal transfer is expected. Polymyxin B: known to cross placenta, with detectable fetal serum levels following maternal administration. |
■ FDA Black Box Warning
None
| Common Effects | Hypersensitivity reactions |
| Serious Effects |
Hypersensitivity to bacitracin or polymyxin BRenal impairment (systemic use)Myasthenia gravis (systemic use due to neuromuscular blockade)Pregnancy (systemic use)
| Precautions | For external use only; avoid contact with eyes, Prolonged use may result in overgrowth of nonsusceptible organisms including fungi, May cause hypersensitivity reactions including contact dermatitis, Use with caution in patients with significant skin damage or absorption risks |
| Food/Dietary | None. This is a topical medication; no food interactions expected. |
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| Breastfeeding |
| Topical application with minimal systemic absorption is likely safe. However, avoid application to the breast area to prevent infant ingestion. Systemic use is contraindicated due to potential infant toxicity. |
| Lactation Rating | L2 - Safer (for topical use); avoid systemic use |
| Teratogenic Risk | No evidence of teratogenicity in animal studies; insufficient human data. Systemic absorption minimal; considered low risk for fetal harm when used topically or ophthalmically. No known adverse effects across all trimesters. |
| Fetal Monitoring | No specific monitoring required due to poor systemic absorption. For prolonged or extensive topical use, monitor for signs of systemic toxicity (nephrotoxicity, neurotoxicity). |
| Fertility Effects | No known effects on fertility in animal or human studies. Minimal systemic absorption precludes significant reproductive impact. |
| Clinical Pearls | Bacitracin zinc/polymyxin B sulfate is a topical antibiotic combination effective against gram-positive organisms (bacitracin) and gram-negative organisms (polymyxin B). It is commonly used for minor wounds, burns, and skin infections. Avoid application to large areas, deep wounds, or severe burns due to risk of systemic absorption and nephrotoxicity. Assess for allergic reactions, especially in patients with known hypersensitivity to bacitracin. Do not use on eyes or mucous membranes. |
| Patient Advice | Apply a thin layer to affected area 2-3 times daily or as directed. · Wash hands before and after application. · Do not use on deep wounds, puncture wounds, animal bites, or serious burns. · Stop use and consult doctor if condition worsens or persists after 1 week. · Seek emergency medical attention if you experience signs of allergic reaction (rash, itching, swelling, severe dizziness, trouble breathing). · Avoid contact with eyes, nose, mouth, or inside of vagina. |