Chemistry - An aminoglycoside antibiotic obtained from Streptomyces fradiae, neomycin is actually a complex of three separate compounds, neomycin A (neamine; inactive), neomycin C and neomycin B (framycetin). The commercially available product almost entirely consists of the sulfate salt of neomycin B. It occurs as an odorless or almost odorless, white to slightly yellow, hygroscopic powder or cryodessicated solid. It is freely soluble in water and very slightly soluble in alcohol. One mg of pure neomycin sulfate is equivalent to not less than 650 Units. Oral or injectable (after reconstitution with normal saline) solutions of neomycin sulfate have a pH from 5-7.5.
Storage/Stability/Compatibility - Neomycin sulfate oral solution should be stored at room temperature (15-30°C) in tight, light-resistant containers. Unless otherwise instructed by the manufacturer, oral tablets/boluses should be stored in tight containers at room temperature. The sterile powder should be stored at room temperature and protected from light. In the dry state, neomycin is stable for at least 2 years at room temperature.
Pharmacology - Neomycin has a mechanism of action and spectrum of activity (primarily gram negative aerobes) similar to the other aminoglycosides, but in comparison to either gentamicin or amikacin, it is significantly less effective against several species of gram negative organisms, including strains of Klebsiella, E. coli and Pseudomonas. However, most strains of neomycin-resistant bacteria of these species remain susceptible to amikacin. More information on the aminoglycosides mechanism of action and spectrum of activity is outlined in more detail in the amikacin monograph.
Uses/Indications - Because neomycin is more nephrotoxic and less effective against several bacterial species than either gentamicin or amikacin, its use is generally limited to the oral treatment of enteral infections, to reduce microbe numbers in the colon prior to colon surgery, and orally or in enema form to reduce ammonia-producing bacteria in the treatment of hepatic encephalopathy. Doses for parenteral administration are listed below, but should be used only with extreme caution due to the drug’s toxic potential.
Pharmacokinetics - Approximately 3% of a dose of neomycin is absorbed after oral or rectal (retention enema) administration, but this can be increased if gut motility is slowed or if the bowel wall is damaged. Therapeutic levels are not attained in the systemic circulation after oral administration.
After IM administration, therapeutic levels can be attained with peak levels occurring within 1 hour of dosing. The drug apparently distributes to tissues and is eliminated like the other aminoglycosides (refer to Amikacin monograph for more details). Orally administered neomycin is nearly all excreted unchanged in the feces.
Contraindications/Precautions/Reproductive Safety - More detailed information on the contraindications, precautions and reproductive safety of the aminoglycoside antibiotics can be found in the amikacin monograph.
Oral neomycin is contraindicated in the presence of intestinal obstruction or if the patient is hypersensitive to aminoglycosides.
Chronic usage of oral aminoglycosides may result in bacterial or fungal superinfections.
Because oral neomycin is only minimally absorbed, it is unlikely significant systemic or teratogenic effects should occur. However, one group of authors (Caprile and Short 1987) recommends that the drug not be used orally in foals.
Adverse Effects/Warnings, Overdosage/Acute Toxicity - Refer to the amikacin monograph for more information regarding these topics with parenteral neomycin. Rarely, oral neomycin may cause ototoxicity, nephrotoxicity, severe diarrhea and intestinal malabsorption.
Drug Interactions, Drug/Laboratory Interactions - Refer to the amikacin monograph for more information regarding drug interactions with parenteral neomycin. In addition: Oral neomycin should not be given concurrently with oral penicillin VK as malabsorption of the penicillin may occur.
Oral neomycin with orally administered digitalis preparations (e.g., digoxin) may result in decreased absorption of the digitalis. Separating the doses of the two medications may not alleviate this effect. Some human patients (<10%) metabolize digoxin in the GI tract and neomycin may increase serum digoxin levels in these patients. It is recommended that if oral neomycin is added or withdrawn from the drug regimen of a patient stabilized on a digitalis glycoside, that enhanced monitoring be performed.
Oral neomycin may decrease the amount of vitamin K absorbed from the gut; this may have ramifications for patients receiving oral anticoagulants. Methotrexate absorption may be reduced by oral neomycin but is increased by oral kanamycin (found in Amforal®).
Although only minimal amounts of neomycin are absorbed after oral or rectal administration, the concurrent use of other ototoxic or nephrotoxic drugs with neomycin should be done with caution.
For oral administration to treat susceptible enteral infections:
a) Adults: 4 - 7.5 g/day PO divided 2-4 times daily at regular intervals. Foals: 2 - 3 g/day PO divided 2-4 times daily at regular intervals. Doses are not standardized; use for general guidance only. (Brander, Pugh, and Bywater 1982)
b) 5 - 15 mg/kg PO once daily (Robinson 1987)
For respiratory tract infections:
a) For pleuritis and less frequently pneumonia: 4.4 mg/kg IM or IV q8-12h. Nephrotoxicity and/or ototoxicity can occur; nephrotoxicity more common in foals. Local myositis seen with IM dosing particularly if treatment is longer than 7 days. Systemic use of oral form is not approved, but is used with penicillin to increase gram negative coverage (Beech 1987b)
Monitoring Parameters -
For oral use:
1) Clinical efficacy
2) Systemic and GI adverse effects with prolonged use
For parenteral use: Refer to Amikacin monograph
Client Information - Clients should understand that the potential exists for severe toxicity (nephrotoxicity, ototoxicity) developing from this medication when used parenterally.
Dosage Forms/Preparations/FDA Approval Status/Withholding Times -
Neomycin Sulfate; Oral Liquid 200 mg/ml
Biosol ® (Upjohn); (OTC) Approved for use in cattle, swine, sheep, turkeys, laying hens, and broilers. Withdrawal times: Cattle = 30 days; Sheep and swine = 20 days, Turkeys and Layers = 14 days; Broilers = 5 days.
Also available as generically labeled products.
Neomycin Sulfate Oral Solution 50 mg/ml in 10 ml dropper bottles
Biosol Aquadrops® (Upjohn); (OTC) Approved for use in dogs and cats.
Neomycin Sulfate Oral Tablets 100 mg
Biosol® Tablets (Upjohn); (OTC) Approved for use in dogs and cats.
Neomycin Sulfate Intrauterine or Oral Boluses 500 mg; Biosol® Boluses (Upjohn); (OTC) Approved for use in cattle, foals, swine, and sheep. Slaughter withdrawal times: Cattle = 30 days; Sheep and swine = 20 days. Milk withdrawal = 48 hours.
Neomycin Sulfate Soluble Powder 3.125 g/ounce;Biosol® Soluble Powder (Upjohn); (OTC) Approved for use in dogs, cats, cattle, swine, sheep, and horses. Slaughter withdrawal times: Cattle = 30 days; Sheep and swine = 20 days.
Neomycin Powder Water/Feed Additive 325 g/lb; Biosol 325® (Upjohn), Neomix Ag® 325 (Upjohn); (OTC) Approved for use in chickens, turkeys, ducks, nonlactating dairy cattle, beef cattle, goats, horses, mink, sheep, and swine. Slaughter withdrawal times: Cattle = 30 days; Sheep and swine = 20 days, Turkeys & layers = 14 days; Broilers = 5 days.
There are several combination neomycin veterinary products, the following are examples:
Neomycin 25 mg, isopropamide 1.67 mg, prochlorperazine 3.33 mg capsules; Neomycin 75 mg, isopropamide 5 mg, prochlorperazine 10 mg capsules; Neo-Darbazine® #1 (Pfizer); (Rx) Approved for use in dogs. Neo-Darbazine® #3 (SKB); (Rx) Approved for use in dogs.
Neomycin Sulfate Oral Tablets 500 mg; Neo-Tabs® (Pharma-Tek) (Rx), generic (Rx)
Neomycin Sulfate Oral Solution 25 mg/ml in pints;Mycifradin® (Upjohn);Neo-fradin® (Pharma-Tek); (Rx)
Disclaimer: the information on this page is used entirely at the