Neomycin
Neomycin sulfate
Also known as: Biosol · Neomix · Neo-325 · Neo-fradin · Neo-Sol 50 · Neovet · Canaural · Soframycin · Neopen · Maxitrol · Nivemycin · fradiomycin sulfate · neomycin sulphate · neomycini sulfas · neomycin B · Framycetin sulphate · Neomycin sulfate · Neomycinum
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Audited v13 dosing evidence
Structured calculator evidenceSusceptible enteric infections (extra-label)
- q6-12h
NA
Governing clinical context (3)
- ■ This medicine may be given by mouth with or without food. If your animal vomits or acts sick after receiving the medicine on an empty stomach, give with food or a small treat to see if this helps.
- Neomycin sulfate oral solution should be stored at room temperature (15°C-30°C [59°F-86°F]) in airtight, light-resistant containers.
- Unless otherwise instructed by the manufacturer, oral tablets/boluses should be stored in airtight containers at room temperature.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Neomycin is a broad-spectrum, bactericidal aminoglycoside antibiotic primarily effective against gram-negative aerobes.
Because it is significantly more nephrotoxic than other aminoglycosides (like gentamicin or amikacin) when given systemically, its use in veterinary medicine is largely restricted to:
- Topical applications (skin, eyes, ears)
- Oral administration for enteric infections or "gut sterilization" prior to surgery
- Hepatic encephalopathy management (to reduce ammonia-producing bacteria in the colon)
Clinical Pearl: Like all aminoglycosides, neomycin exhibits concentration-dependent bactericidal activity and a significant post-antibiotic effect (PAE). However, it is poorly absorbed from an intact gastrointestinal tract (only ~3%), making it ideal for local action within the gut lumen while minimizing systemic toxicity.
Mechanism of action
Neomycin actively transports across the bacterial cell membrane (an oxygen-dependent process, hence its lack of efficacy against anaerobes). It irreversibly binds to the 30S ribosomal subunit → causes misreading of mRNA → inhibits protein synthesis → leads to rapid bacterial cell death.
Safety & warnings
Contraindications
- Intestinal obstruction (for oral use)
- Rabbits and hares (disrupts GI flora)
- Neonates (avoid oral use due to higher systemic absorption)
- Animals with a perforated tympanic membrane (eardrum)
- Concurrent use with other known ototoxic products
- Known hypersensitivity to aminoglycosides
- Pre-existing renal disease (for systemic use)
- Ruptured tympanic membrane (for otic preparations)
Adverse effects
- Nephrotoxicity (severe if given parenterally)
- Ototoxicity (irreversible, parenteral or rarely oral)
- Severe diarrhea
- Intestinal malabsorption
- GI superinfections (with chronic oral use)
- Ototoxicity (deafness)
- Vestibular toxicity (ataxia, head tilt, nystagmus)
- Local irritation or erythema at the application site
- Ototoxicity (vestibular and auditory)
- Severe diarrhoea or malabsorption syndrome (oral use)
- Bacterial or fungal superinfections
- Local irritation (topical ophthalmic use)
Precautions
Use with extreme caution in patients with renal dysfunction, even when given orally, as a small percentage is absorbed. Avoid parenteral use in working dogs due to the risk of irreversible ototoxicity. Use cautiously in patients with neuromuscular disorders (e.g., myasthenia gravis) due to the neuromuscular blocking activity of aminoglycosides. Geriatric and neonatal animals require careful monitoring and dosage adjustments if systemic absorption is expected.
Drug interactions
Oral neomycin may decrease digoxin absorption. In a small subset of patients who metabolize digoxin in the GI tract, neomycin may increase serum digoxin levels.
Absorption may be reduced by oral neomycin.
Concurrent use increases the risk of additive toxicity, even with oral neomycin, and should be done with caution.
Concurrent use may cause malabsorption of the penicillin.
Oral neomycin may decrease vitamin K absorption from the gut, potentially increasing anticoagulant effects.
Increased risk of cumulative ototoxicity (deafness and vestibular dysfunction)
Decreased absorption of potassium
Decreased absorption of vitamin K
Synergistic ototoxicity and nephrotoxicity
Monitoring
- Clinical efficacy
- Systemic and GI adverse effects with prolonged use
- Renal function parameters (BUN, creatinine, urinalysis) if used parenterally
- Resolution of clinical signs of otitis
- Integrity of the tympanic membrane (via otoscopy)
- Hearing function and vestibular signs (head tilt, ataxia, nystagmus)
- Renal function (BUN, Creatinine, Urinalysis for casts/protein)
- Hearing and vestibular function (head tilt, nystagmus, ataxia)
- Gastrointestinal signs (diarrhoea)
Pharmacokinetics
Half-life
Absorption
Approximately 3% of a dose is absorbed after oral or rectal administration. Absorption increases if gut motility is slowed or if the bowel wall is damaged. Therapeutic systemic levels are not attained via oral administration.
Distribution
Distributes to tissues similarly to other aminoglycosides. Does not cross the blood-brain barrier well.
Metabolism
Not significantly metabolized.
Elimination
Orally administered neomycin is nearly all excreted unchanged in the feces. Parenterally administered drug is eliminated primarily through renal mechanisms.
Overdose
Parenteral overdosage carries a high risk of severe nephrotoxicity and ototoxicity. Oral overdosage is less likely to cause systemic toxicity unless the gut wall is compromised, but can lead to severe diarrhea and malabsorption.
Available products
Formulations
- Oral liquid
- Soluble powder
- Oral tablets
- Topical formulations (ophthalmic, otic, dermatologic)
- Topical: 5 mg/g suspension (often combined with fusidic acid, nystatin, and prednisolone as Canaural)
- Oral: 500 mg tablets
- Parenteral: 100 mg/ml neomycin combined with 200 mg/ml penicillin G
- Topical: 0.25-0.5% dermatological, ophthalmic, and otic preparations
Veterinary
- Neomycin Sulfate Oral Liquid: 200 mg/mL
- Neomycin Sulfate Soluble Powder: 325 grams/lb (Neo-325, Neovet 325/100, Neo-Sol 50)
- Canaural Ear Drops (Framycetin 5 mg/g, Fusidic acid 5 mg/g, Nystatin 100,000 IU/g, Prednisolone 2.5 mg/g)
- Neopen (100 mg/ml neomycin + 200 mg/ml penicillin G injection)
Human-labeled
- Neomycin Sulfate Tablets: 500 mg
- Neomycin Sulfate Oral Solution: 25 mg/mL (Neo-fradin)
- Soframycin (Framycetin sulfate 1% topical/ophthalmic preparations - availability varies by region)
- Nivemycin (500 mg tablets)
- Maxitrol (ophthalmic drops/ointment)
Regulatory status
Subject to responsible antimicrobial use guidelines.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store oral solutions and tablets at room temperature (15-30°C) in tight, light-resistant containers. In the dry state, neomycin is stable for at least 2 years at room temperature.
Client information
- Oral Use: May cause diarrhea or alter normal gut flora. Follow your veterinarian's instructions carefully.
- Toxicity Warning: If this medication is given by injection, there is a significant risk of kidney damage (nephrotoxicity) and hearing loss/balance issues (ototoxicity).
- Ensure your pet has access to plenty of fresh water.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.