BACITRACIN ZINC AND 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 interfering with dephosphorylation of the lipid carrier that transports peptidoglycan precursors across the cell membrane. Polymyxin B sulfate disrupts bacterial cell membrane integrity by interacting with lipopolysaccharides and phospholipids, increasing permeability and causing cell death.
| Metabolism | Bacitracin zinc is minimally absorbed; not significantly metabolized. Polymyxin B sulfate is not significantly metabolized systemically. |
| Excretion | Bacitracin zinc is primarily excreted unchanged in urine via glomerular filtration; polymyxin B sulfate is excreted slowly via renal filtration (approximately 60% over 72 hours) with the remainder eliminated via nonrenal pathways (biliary/fecal). |
| Half-life | Bacitracin: approximately 1.5 hours in patients with normal renal function; prolonged in renal impairment. Polymyxin B: approximately 9.7 hours (range 6–13 hours); half-life extends significantly in renal dysfunction requiring dose adjustment. |
| Protein binding | Bacitracin: negligible (<5%) protein binding. Polymyxin B: approximately 55–60% bound to plasma proteins. |
| Volume of Distribution | Polymyxin B: approximately 0.44 L/kg (range 0.27–0.74 L/kg), indicating distribution primarily in extracellular fluid; bacitracin: minimal systemic Vd (not clinically relevant due to topical use). |
| Bioavailability | Bacitracin zinc and polymyxin B sulfate are not systemically absorbed following topical application to intact skin; bioavailability is negligible (<0.1%). |
| Onset of Action | Topical application: antibacterial effect begins within minutes of application; systemic absorption is minimal with intact skin. |
| Duration of Action | Duration of antibacterial effect following topical application is approximately 6–12 hours; reapplication is recommended twice daily for sustained effect. |
Apply topically to affected area 2 to 4 times daily.
| Dosage form | OINTMENT |
| Renal impairment | No systemic absorption; no adjustment required. |
| Liver impairment | No systemic absorption; no adjustment required. |
| Pediatric use | Same as adult: apply topically to affected area 2 to 4 times daily. |
| Geriatric use | Same as adult; no specific adjustments needed. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
No significant systemic drug interactions due to minimal absorption For topical use only not for eyes or deep wounds.
| FDA category | Animal |
| Breastfeeding | Breastfeeding safety: Topical use is considered compatible with breastfeeding due to negligible systemic absorption. M/P ratio is unknown and not calculable for topical formulation. Systemic levels are too low to produce measurable drug in breast milk. Caution with open wounds or extensive application may increase absorption. |
| Teratogenic Risk |
■ FDA Black Box Warning
None.
| Common Effects | Hypersensitivity reactions |
| Serious Effects |
Hypersensitivity to bacitracin, polymyxin B, or any component of the formulation.
| Precautions | For external use only. Avoid contact with eyes. May cause hypersensitivity reactions (e.g., rash, itching). Prolonged use may lead to overgrowth of nonsusceptible organisms. Use with caution in patients with renal impairment if large areas are treated. |
| Food/Dietary | No known food-drug interactions for this topical preparation. Systemic absorption is minimal with topical application to intact skin, but patients with extensive skin disruption should avoid alcohol or other topical irritants that may enhance absorption. |
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| Topical bacitracin zinc and polymyxin B sulfate use during pregnancy is not associated with known teratogenicity. No fetal risks have been demonstrated in animal studies or human reports for ophthalmic or topical routes. Systemic absorption is minimal, further reducing risk. FDA Pregnancy Category C for polymyxin B (insufficient data); bacitracin is generally considered low risk topically. No trimester-specific risks identified. |
| Fetal Monitoring | No specific maternal or fetal monitoring is required for topical bacitracin zinc and polymyxin B sulfate. For ophthalmic use, standard prenatal care is sufficient. Monitor for rare allergic reactions (topical sensitization) in mother. |
| Fertility Effects | No known adverse effects on fertility based on animal reproduction studies with bacitracin and polymyxin B. Topical application does not impact reproductive function in humans. |
| Clinical Pearls | This fixed-dose combination (Bacitracin Zinc 500 U/g + Polymyxin B Sulfate 10,000 U/g) is a topical triple-antibiotic ointment alternative. Avoid use in deep puncture wounds or severe burns due to risk of systemic absorption and nephrotoxicity from bacitracin. Monitor for allergic contact dermatitis, which can present as worsening rash despite treatment. Do not use in eyes or on mucous membranes. Effective against Gram-positive (bactiracin) and Gram-negative (polymyxin B) organisms; no anti-pseudomonal activity. |
| Patient Advice | Apply a thin layer to the affected area 1-3 times daily as directed. · Clean the wound with sterile saline before each application. · Do not use on large areas, deep wounds, or severe burns without medical supervision. · Stop use and consult a doctor if redness, swelling, or irritation persists or worsens after 7 days. · Avoid contact with eyes, nose, mouth, or other mucous membranes; rinse thoroughly with water if accidental contact occurs. · Store at room temperature, away from moisture and heat. |