NEOMYCIN SULFATE AND POLYMYXIN B SULFATE GRAMICIDIN
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, inhibiting bacterial protein synthesis. Polymyxin B is a polypeptide antibiotic that disrupts bacterial cell membrane permeability by interacting with phospholipids. Gramicidin is a polypeptide antibiotic that increases cell membrane permeability by forming ion channels, leading to bacterial cell death.
| Metabolism | Neomycin is minimally absorbed after topical application and is excreted unchanged in the urine. Polymyxin B is not significantly absorbed. Gramicidin is not systemically absorbed. |
| Excretion | Renal: ~95% for neomycin (unchanged), minimal for polymyxin B (1-10% unchanged) and gramicidin (<1%). Fecal: 50-60% for polymyxin B (biliary), ~1% for neomycin. |
| Half-life | Neomycin: 2-3 hours (normal renal function); polymyxin B: 6-8 hours; gramicidin: ~10 hours (estimated from topical absorption). Prolonged in renal impairment, especially for polymyxin B. |
| Protein binding | Neomycin: 0-30% (low); polymyxin B: 80-90% (alpha-1-acid glycoprotein, albumin); gramicidin: 50-70% (albumin). |
| Volume of Distribution | Neomycin: 0.25-0.4 L/kg (extracellular water); polymyxin B: 0.3-0.6 L/kg (limited tissue penetration); gramicidin: 0.5-0.8 L/kg (estimated, based on topical data). |
| Bioavailability | Oral: <3% for neomycin and polymyxin B (<1% for gramicidin); topical/ophthalmic/otic: 100% (local). No IV formulation. |
| Onset of Action | Topical ophthalmic: 15-30 minutes; otic: 24-48 hours for full effect; topical dermatological: 2-3 days for improvement. |
| Duration of Action | Ophthalmic: 4-6 hours between doses; otic: sustained with q.i.d. dosing; topical dermatological: 12-24 hours after application. |
Instill 2 drops (or appropriate amount) into affected eye(s) every 2-4 hours for 7-10 days. Frequency may be increased to every 1-2 hours in severe infections. Ophthalmic suspension, not for injection.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No systemic absorption; renal adjustment not required. |
| Liver impairment | No systemic absorption; hepatic adjustment not required. |
| Pediatric use | Same as adult dosing; 1-2 drops into affected eye(s) every 2-4 hours. Use with caution in neonates due to potential for systemic absorption through ocular mucosa. |
| Geriatric use | Same as adult dosing; no specific adjustments needed. Monitor for local adverse effects. |
| 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 | Unknown if topical neomycin, polymyxin B, or gramicidin are excreted in human milk; systemic absorption is minimal. Caution should be exercised. M/P ratio not available. |
| Teratogenic Risk | Neomycin sulfate, polymyxin B sulfate, and gramicidin are poorly absorbed via topical/ophthalmic/otic routes; systemic exposure is negligible. No adequate and well-controlled studies in pregnant women. Animal reproduction studies for the combination are lacking. However, topical aminoglycosides are not associated with increased risk of congenital anomalies. Fetal risk is considered minimal when used as directed. Avoid use for extended periods or on large areas of broken skin. |
■ FDA Black Box Warning
None
| Common Effects | topical infections |
| Serious Effects |
["Hypersensitivity to any component","Perforated tympanic membrane (for otic use)","Viral or fungal infections","Large denuded areas or extensive burns"]
| Precautions | ["Prolonged use may result in overgrowth of nonsusceptible organisms including fungi","Potential for ototoxicity and nephrotoxicity if applied to large areas or broken skin","Hypersensitivity reactions","Cross-sensitivity with other aminoglycosides"] |
Loading safety data…
| Fetal Monitoring | No specific monitoring required beyond routine prenatal care due to negligible systemic absorption. Observe for signs of skin irritation or allergic reaction at application site. |
| Fertility Effects | No data exist on effects of topical neomycin/polymyxin B/gramicidin on fertility. Systemic aminoglycosides may cause testicular damage in animals; relevance to topical use is unknown. |