NEOMYCIN AND POLYMYXIN B SULFATE
Clinical safety rating: safe
Other nephrotoxic or ototoxic drugs increase risk of toxicity Can cause ototoxicity and nephrotoxicity with systemic use.
Neomycin is an aminoglycoside antibiotic that binds to the 30S ribosomal subunit, causing misreading of mRNA and inhibiting protein synthesis. Polymyxin B sulfate is a cationic detergent that disrupts bacterial cell membrane permeability by interacting with phospholipids, leading to cell death.
| Metabolism | Neomycin is minimally absorbed after topical application; absorbed fraction is primarily excreted unchanged by the kidneys. Polymyxin B is also minimally absorbed; systemic metabolism is negligible. |
| Excretion | Renal: ~90-95% (neomycin, polymyxin B) unchanged; fecal: 5-10% (biliary excretion negligible). |
| Half-life | Neomycin: 2-3 hours (normal renal function), prolonged to 24-48 hours in renal impairment; Polymyxin B: 4.5-6 hours (normal renal function), extended significantly in renal failure. |
| Protein binding | Neomycin: negligible (<10%); Polymyxin B: moderate (50-60%), primarily to albumin. |
| Volume of Distribution | Neomycin: 0.2-0.3 L/kg (mainly extracellular); Polymyxin B: 0.6-0.8 L/kg (distributes to extravascular tissues, low CNS penetration). |
| Bioavailability | Oral: <3% (local effect only, minimal systemic absorption); Topical/ophthalmic/irrigation: negligible (<1% systemic). |
| Onset of Action | Oral: 1-2 hours (local GI effect); Topical: minutes (local antibacterial); Ophthalmic: 15-30 minutes; Irrigation: immediate. |
| Duration of Action | Oral: 6-12 hours (local); Topical/ophthalmic: 6-8 hours; Irrigation: varies with irrigation rate; renal elimination limits duration systemically. |
For irrigation of urinary bladder: 1 mL of solution containing 40 mg neomycin and 200,000 units polymyxin B per mL diluted in 1 liter of 0.9% sodium chloride, instilled via continuous irrigation at a rate of 1 liter per 24 hours. For topical use: apply thin layer to affected area 2-4 times daily.
| Dosage form | SOLUTION |
| Renal impairment | Neomycin is significantly excreted renally; accumulation may occur in renal impairment. Avoid systemic use in renal failure (CrCl <30 mL/min). For topical or irrigation use, risk of systemic absorption is low but caution is advised in severe renal impairment. |
| Liver impairment | No dosage adjustment required for hepatic impairment. Neomycin is not metabolized by the liver and is excreted renally. |
| Pediatric use | Neomycin and polymyxin B sulfate for bladder irrigation: not established in pediatric patients. For topical use: apply thin layer to affected area 2-4 times daily. Safety and efficacy not established for systemic use in children. |
| Geriatric use | Use with caution due to age-related renal impairment. Monitor renal function and consider dose reduction if using prolonged irrigation. For topical use, no specific adjustment needed but avoid application to large areas or broken skin. |
| 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.
| FDA category | Animal |
| Breastfeeding | Excreted in breast milk in trace amounts due to poor absorption. M/P ratio not established. Considered compatible with breastfeeding; risk to infant minimal due to limited systemic absorption. Monitor infant for diarrhea, rash, or changes in stool consistency. |
| Teratogenic Risk | FDA Pregnancy Category D for neomycin; polymyxin B is Category C. Both cross placenta. First trimester: potential ototoxicity and nephrotoxicity minimal due to poor absorption; systemic exposure from topical use negligible. Second and third trimesters: theoretical risk of fetal ototoxicity and nephrotoxicity if significant maternal systemic absorption occurs. Data insufficient to quantify risk. |
■ FDA Black Box Warning
Neomycin is potentially nephrotoxic and ototoxic (vestibular and cochlear). The risk is increased in patients with renal impairment, pre-existing hearing loss, or prolonged use. Polymyxin B can cause nephrotoxicity and neurotoxicity. Combined use of neomycin and polymyxin B may increase these risks.
| Common Effects | topical infections |
| Serious Effects |
["Hypersensitivity to neomycin, polymyxin B, or any component of the formulation.","Patients with known aminoglycoside hypersensitivity.","Viral or fungal ocular infections (unless concomitant bacterial infection is present).","Use in eyes with epithelial damage (relative contraindication due to potential toxicity)."]
| Precautions | ["Prolonged use may result in overgrowth of nonsusceptible organisms including fungi.","Cross-allergenicity among aminoglycosides may occur.","Ophthalmic use only; not for injection or irrigation.","Discontinue if sensitivity or irritation occurs.","Caution in patients with renal impairment or myasthenia gravis due to potential neuromuscular blockade."] |
Loading safety data…
| Fetal Monitoring | Monitor maternal renal function (serum creatinine, BUN) and hearing if prolonged treatment or underlying renal impairment. For fetal monitoring, standard antenatal surveillance. Assess for signs of ototoxicity or nephrotoxicity in neonate if maternal toxicity suspected. |
| Fertility Effects | No known direct effects on fertility. Animal studies with neomycin showed no impairment. Systemic absorption minimal; unlikely to affect reproductive organs or gametes. |