BACITRACIN-NEOMYCIN-POLYMYXIN
Clinical safety rating: safe
Other nephrotoxic or ototoxic drugs increase risk of toxicity Can cause ototoxicity and nephrotoxicity with systemic use.
Bacitracin inhibits bacterial cell wall synthesis by interfering with dephosphorylation of the lipid carrier that transports peptidoglycan precursors. Neomycin and polymyxin B are aminoglycoside and polypeptide antibiotics, respectively; neomycin binds to the 30S ribosomal subunit, causing misreading of mRNA and inhibiting protein synthesis, while polymyxin B disrupts bacterial cell membrane integrity by interacting with lipopolysaccharides and phospholipids, leading to increased permeability and cell death.
| Metabolism | Not extensively metabolized. Systemic absorption from topical application is minimal; absorbed drug may undergo hepatic metabolism or be excreted renally unchanged. |
| Excretion | Bacitracin: primarily renal (>90% unchanged); Neomycin: renal (30-50% unchanged) with non-renal clearance; Polymyxin: renal excretion of parent drug (60-80% unchanged) with some biliary and fecal elimination. |
| Half-life | Bacitracin: 1.5 hours (prolonged in renal impairment); Neomycin: 2-3 hours (accumulates with renal dysfunction); Polymyxin B: 6-9 hours (increased in renal impairment). |
| Protein binding | Bacitracin: <10% bound to plasma proteins; Neomycin: 0-30% bound; Polymyxin B: 50-70% bound, primarily to alpha-1-acid glycoprotein and lipoproteins. |
| Volume of Distribution | Bacitracin: 0.3 L/kg (confined to extracellular fluid); Neomycin: 0.2-0.3 L/kg (low tissue penetration except renal cortex); Polymyxin B: 0.7-1.0 L/kg (extensive tissue binding). |
| Bioavailability | Oral: negligible (<1%) for all three components; topical: minimal systemic absorption via intact skin (<0.5%); ophthalmic/otic: minimal absorption via mucosal surfaces. |
| Onset of Action | Topical application: within 24-48 hours for bacterial inhibition; ophthalmic: 1-2 hours; otic: 30-60 minutes; systemic administration (not recommended): immediate. |
| Duration of Action | Topical: 6-8 hours, requires multiple daily applications; ophthalmic: 3-6 hours; otic: 4-6 hours. Systemic: not applicable. |
| Molecular Weight | 1422.69 |
Apply topically to affected area 2-5 times daily.
| Dosage form | OINTMENT |
| Renal impairment | No systemic absorption; no dosage adjustment required. |
| Liver impairment | No systemic absorption; no dosage adjustment required. |
| Pediatric use | Apply topically to affected area 2-5 times daily; same as adult dose. |
| Geriatric use | Apply topically to affected area 2-5 times daily; same as adult dose. |
| 1st trimester | Topical use considered safe; systemic absorption minimal. Avoid ophthalmic use if membranes ruptured due to risk of ototoxicity. |
| 2nd trimester | Same as T1. |
| 3rd trimester | Same as T1. |
Clinical note
Other nephrotoxic or ototoxic drugs increase risk of toxicity Can cause ototoxicity and nephrotoxicity with systemic use.
| FDA category | Animal |
| Placental transfer | Negligible for topical/ophthalmic use; systemic absorption minimal. Bacitracin and polymyxin B cross placenta in small amounts; neomycin may cross but absorption is low. |
| Breastfeeding | Minimal systemic absorption from topical/ophthalmic use; considered compatible with breastfeeding. Avoid application to breast area to prevent infant ingestion. |
■ FDA Black Box Warning
Not applicable for topical formulations. However, systemic use of bacitracin (rare) may cause nephrotoxicity and anaphylactic reactions. Neomycin may cause ototoxicity and nephrotoxicity with systemic absorption.
| Common Effects | topical infections |
| Serious Effects |
Hypersensitivity to any componentMyasthenia gravis (systemic use)Renal impairment (systemic use)
| Precautions | Prolonged use may result in overgrowth of nonsusceptible organisms including fungi., Topical use may cause allergic contact dermatitis, especially with neomycin., Avoid application to large areas, open wounds, or damaged skin due to potential systemic absorption and toxicity., Use with caution in patients with renal impairment or pre-existing hearing loss (neomycin component)., Ototoxicity and nephrotoxicity may occur if significant systemic absorption occurs. |
| Food/Dietary |
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| Lactation Rating | L2 (Probably Compatible) |
| Teratogenic Risk | Bacitracin-Neomycin-Polymyxin is a topical combination with negligible systemic absorption; thus, fetal risk is minimal. No known teratogenic effects reported; animal studies for individual components show no fetal harm at systemic doses. However, neomycin has theoretical risk of ototoxicity if systemically absorbed, but topical use is considered low risk. FDA Pregnancy Category C for components, but topical use deemed safe. |
| Fetal Monitoring | No specific monitoring required due to topical application. If used on large areas or damaged skin, monitor for systemic effects (e.g., nephrotoxicity from bacitracin, ototoxicity from neomycin). |
| Fertility Effects | No known effects on fertility with topical use. Systemic neomycin may impair testicular function, but unlikely with topical application. |
| No significant food interactions; topical application minimizes systemic absorption. No dietary restrictions. |
| Clinical Pearls | Triple antibiotic ointment (bactiracin-neomycin-polymyxin) is first-line for prophylaxis of minor skin infections; avoid use on large areas, deep wounds, or burns due to risk of systemic absorption and nephrotoxicity. Neomycin carries high risk of allergic contact dermatitis; consider alternative in patients with known hypersensitivity. Topical use only; not for ophthalmic or intranasal application due to polymyxin ocular toxicity. Synergistic coverage includes Gram-positive (bacitracin), Gram-negative (polymyxin), and broad-spectrum (neomycin). |
| Patient Advice | Apply a thin layer to clean, minor cuts, scrapes, or burns 1-3 times daily. · Do not use on large body areas, deep puncture wounds, animal bites, or serious burns. · Stop use and consult doctor if rash, irritation, or signs of infection (worsening redness, swelling, pus) develop. · Avoid use on eyes, nose, or mouth; if contact occurs, rinse thoroughly with water. · Tell your doctor if you have kidney problems or are allergic to any of the ingredients (bacitracin, neomycin, polymyxin B). |