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Aminoglycoside antibiotic (topical/oral)

Neomycin sulfate

Neomycin sulfate is an aminoglycoside antibacterial used topically, in ear and eye preparations, and orally for bowel decontamination as it is poorly absorbed from the gut.

Adult dose

Dose: Hepatic coma (portal-systemic encephalopathy), adjunctive therapy: 4 to 12 g/day of neomycin sulfate (eight to 24 tablets of 500 mg) in divided doses
Route: Oral (tablets)
Frequency: Divided doses (the number of doses per day is not stated in the label); treatment continued over a period of five to six days
Scope: this US label covers ORAL neomycin sulfate tablets only (500 mg, equivalent to 350 mg neomycin base). The page's route is PO/Topical, and the page's oral hepatic-encephalopathy use matches this label; no topical or otic dose is written because none is in this label. REGIMEN (label): 'For use as an adjunct in the management of hepatic coma, the recommended dose is 4 to 12 grams per day given in the following regimen: Withdraw protein from diet. Avoid use of diuretic agents. Give supportive therapy, including blood products, as indicated. Give neomycin sulfate tablets in doses of 4 to 12 grams of neomycin sulfate per day (eight to 24 tablets) in divided doses. Treatment should be continued over a period of five to six days, during which time protein should be returned incrementally to the diet.' CHRONIC HEPATIC INSUFFICIENCY: 'If less potentially toxic drugs cannot be used for chronic hepatic insufficiency, neomycin in doses of up to four grams daily (eight tablets per day) may be necessary.' DURATION AND TOXICITY: 'To minimize the risk of toxicity, use the lowest possible dose and the shortest possible treatment period to control the condition. Treatment for periods longer than two weeks is not recommended.' The risk of neomycin-induced toxicity progressively increases when treatment must be extended in a patient with hepatic encephalopathy who has failed to fully respond; frequent periodic monitoring for drug toxicity is mandatory and neomycin serum concentrations should be monitored to avoid potentially toxic levels; the benefits should be weighed against the risks of nephrotoxicity, permanent ototoxicity and neuromuscular blockade following accumulation of neomycin in the tissues. SUPPRESSION OF INTESTINAL BACTERIA (second labelled indication, adjunctive therapy e.g. preoperative preparation of the bowel, given concomitantly with erythromycin enteric-coated base): the label gives an example regimen for preoperative prophylaxis for elective colorectal surgery (proposed surgery time 8:00 a.m.) in which, on pre-op day 1, neomycin sulfate (1 g) and erythromycin base (1 g) are given orally at 1:00 p.m., 2:00 p.m. and 11:00 p.m., together with the label's diet, bisacodyl, magnesium sulfate (30 mL of 50% solution, 15 g) and enema steps; it is an example regimen, not a stated standard dose. No maximum dose is printed as such in the label (none written). Children: no paediatric dose is stated in the label sections retrieved. No UK SPC for neomycin sulfate is listed on eMC — this dose is from US prescribing information (Neomycin Sulfate Tablets USP, Chartwell RX) and must be verified against UK practice.

Dose adjustments

Renal

No dose adjustment is stated in the US label. The risk of nephrotoxicity and ototoxicity is greater in patients with impaired renal function; serial vestibular and audiometric tests, as well as tests of renal function, should be performed (especially in high-risk patients); neomycin serum concentrations should be monitored in hepatic coma treatment to avoid potentially toxic levels.

Dose independently re-sourced from US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Intestinal obstruction
  • History of hypersensitivity to the drug
  • Patients with a history of hypersensitivity or serious toxic reaction to other aminoglycosides may have a cross-sensitivity to neomycin
  • Inflammatory or ulcerative gastrointestinal disease (potential for enhanced gastrointestinal absorption of neomycin)

Side effects

  • Most common: nausea, vomiting and diarrhea
  • Malabsorption syndrome (increased fecal fat, decreased serum carotene, fall in xylose absorption) reported with prolonged therapy
  • Nephrotoxicity and neurotoxicity including ototoxicity have been reported following oral use, even when used in recommended doses
  • Permanent bilateral auditory ototoxicity and sometimes vestibular toxicity; ototoxicity is often delayed in onset and patients developing cochlear damage will not have symptoms during therapy to warn them, so deafness may occur long after neomycin has been discontinued
  • Neuromuscular blockade and respiratory paralysis reported following oral use (calcium salts may reverse these phenomena, but mechanical respiratory assistance may be necessary)
  • Systemic absorption occurs following oral administration and toxic reactions may occur

Interactions

  • Other aminoglycosides (including paromomycin) and other potentially nephrotoxic and/or neurotoxic drugs such as bacitracin, cisplatin, vancomycin, amphotericin B, polymyxin B, colistin and viomycin: concurrent and/or sequential use should be avoided because toxicity may be additive
  • Potent diuretics such as ethacrynic acid or furosemide: concurrent use should be avoided (diuretics alone may cause ototoxicity; intravenous diuretics may enhance neomycin toxicity by altering antibiotic concentration in serum and tissue)
  • Anesthetics and neuromuscular blocking agents such as tubocurarine, succinylcholine and decamethonium, or massive transfusions of citrate anticoagulated blood: the possibility of neuromuscular blockade and respiratory paralysis should be considered
  • Erythromycin (enteric-coated base or base): given concomitantly with neomycin as part of the labelled bowel-suppression regimen

Monitoring

  • Close clinical observation because of the potential toxicity
  • Serial vestibular and audiometric tests, as well as tests of renal function, especially in high-risk patients
  • Neomycin serum concentrations, to avoid potentially toxic levels
  • Frequent periodic monitoring for drug toxicity in hepatic encephalopathy patients whose treatment must be extended
  • Additional risk factors for toxicity: impaired renal function, advanced age and dehydration

Clinical monograph

How it works

It binds to the bacterial 30S ribosomal subunit, causing misreading of messenger RNA and inhibiting protein synthesis to produce a bactericidal effect against many Gram-negative organisms.

Prescribing in practice

  • Systemic absorption (for example from broken skin, large surface areas or in renal impairment) can cause irreversible ototoxicity and nephrotoxicity, so prolonged or extensive use should be avoided.
  • It is too toxic for parenteral use and is reserved for topical or oral local effect.
  • Topical use can cause contact sensitisation, and cross-sensitivity with other aminoglycosides may occur.

Monitoring

Watch for signs of hearing loss or balance disturbance with prolonged or oral use, particularly in renal impairment or the elderly.

Counselling the patient

  • Report any hearing changes, ringing in the ears or dizziness.
  • Do not apply to large raw areas or use for longer than advised.

Evidence & guidelines

The ototoxic and nephrotoxic potential of aminoglycosides is well established and documented in current prescribing references.

Reference: NICE; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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