neomycin sulfate
Mycifradin, Myciguent, Neo-Fradin, Neo-Tab

Available forms
Available by prescription only
Oral solution: 125 mg/5 ml
Otic suspension: 5 mg/ml (with polymyxin B sulfate 10,000 units/ml and hydrocortisone 1%)
Tablets: 500 mg
Available without a prescription
Cream: 0.5%
Ointment: 0.5%

Indications and dosages
 Infectious diarrhea caused by enteropathogenic Escherichia coli. Adults: 50 mg/kg P.O. daily in four divided doses for 2 to 3 days.
Children: 50 to 100 mg/kg P.O. daily divided q 4 to 6 hours for 2 to 3 days.
 Suppression of intestinal bacteria preoperatively. Adults: 1 g P.O. q 1 hour for four doses; then 1 g q 4 hours for rest of 24 hours. A saline cathartic should precede therapy.
Children: 40 to 100 mg/kg P.O. daily divided q 4 to 6 hours. First dose should be preceded by saline cathartic.
2- to 3-day regimen. Adults and children: 88 mg/kg P.O. in six equally divided doses at 4-hour intervals. Or, for 8 a.m. surgery, 1 g of neomycin and 1 g of erythromycin base P.O. at 1 p.m., 2 p.m., and 11 p.m. on the day preceding the surgery.
 Adjunctive treatment in hepatic coma. Adults: 1 to 3 g P.O. q.i.d. for 5 to 6 days; 200 ml of 1% or 100 ml of 2% solution as enema retained for 20 to 60 minutes q 6 hours.
Children: 50 to 100 mg/kg P.O. daily in divided doses for 5 to 6 days.
 Treatment of hypercholesterolemia ◇. Adults: 500 mg to 2 g P.O. daily in two or three divided doses.
 External ear canal infection. Adults and children: 2 to 5 drops into ear canal t.i.d. or q.i.d. for 7 to 10 days.
 Topical bacterial infections, burns, wounds, skin grafts, following surgical procedure, lesions, pruritus, trophic ulcerations, and edema. Adults and children: Rub in small amount gently b.i.d., t.i.d., or as directed.
≡ Dosage adjustment. Use reduced dosage in adults and children with renal failure. Specific recommendations aren’t available.

Pharmacodynamics
Antibiotic action: Neomycin is bactericidal; it binds directly to the 30S ribosomal subunit, thus inhibiting bacterial protein synthesis. Its spectrum of action includes many aerobic gram-negative organisms and some aerobic gram-positive organisms. Drug is far less active against many gram-negative organisms than are amikacin, gentamicin, netilmicin, and tobramycin. Given orally or as retention enema, neomycin inhibits ammonia-forming bacteria in the GI tract, reducing ammonia and improving neurologic status of patients with hepatic encephalopathy. It’s rarely given systemically because of its high potential for ototoxicity and nephrotoxicity.

Pharmacokinetics
Absorption: About 3% absorbed after oral use, although absorption is enhanced in patients with impaired GI motility or mucosal intestinal ulcerations. Neomycin isn’t absorbed through intact skin; it may be absorbed from wounds, burns, or skin ulcers.
Distribution: Crosses the placental barrier. Oral administration restricts distribution to the GI tract.
Metabolism: Not metabolized.
Excretion: Excreted primarily in urine by glomerular filtration. Elimination half-life in adults is 2 to 3 hours; in severe renal damage, half-life may extend to 24 hours. After oral administration, neomycin is excreted primarily unchanged in feces.

Contraindications and precautions
Contraindicated in patients hypersensitive to drug. Oral form contraindicated in patients sensitive to other aminoglycosides and in those with intestinal obstruction. Don’t give drug parenterally.
  Use oral form cautiously in elderly patients and patients with impaired renal function, neuromuscular disorders, or ulcerative bowel lesions. Use topical form cautiously in patients with extensive skin conditions.

Interactions
Drug-drug. Digoxin, methotrexate: May decrease digoxin and methotrexate absorption. Monitor serum levels.
Neuromuscular blockers: Enhances action of neuromuscular blockers. Avoid use together.
Oral anticoagulants: Potentiates effects of anticoagulant. Dosage adjustment of anticoagulants may be needed.

Adverse reactions
EENT: ototoxicity with oral use.
GI: nausea, vomiting, diarrhea, malabsorption syndrome, and Clostridium difficile-related colitis with oral use.
GU: nephrotoxicity with oral use.
Musculoskeletal: neuromuscular blockadewith topical use.
Skin: rash, contact dermatitis, and urticaria with topical use.

Effects on lab test results
• Increased BUN, creatinine, and nonprotein nitrogen levels.

Overdose and treatment
Overdose may cause ototoxicity, nephrotoxicity, and neuromuscular toxicity.
 After recent ingestion (4 hours or less), empty patient’s stomach by induced emesis or gastric lavage; follow with activated charcoal to reduce absorption. Remove drug by hemodialysis or peritoneal dialysis; treatment with calcium salts or anticholinesterases reverses neuromuscular blockade.

Special considerations
• Monitor renal function: output, specific gravity, urinalysis, BUN and creatinine levels, and creatinine clearance during therapy.
• Evaluate patient’s hearing before and during prolonged therapy. Onset of deafness may occur several weeks after drug is stopped.
• Watch for superinfection, such as fever or other evidence of new infection.
• In adjunctive treatment of hepatic coma, decrease patient’s dietary protein and assess neurologic status frequently during therapy.
• Monitor patient for hypersensitivity or contact dermatitis.
• The ototoxic and nephrotoxic properties of neomycin limit its usefulness.
• Neomycin is nonabsorbable at recommended dosage. However, more than 4 g daily may be systemically absorbed and lead to nephrotoxicity.
• Drug is available with polymyxin B as a bladder irrigant.
Preoperative bowel contamination
• Provide low-residue diet and cathartic immediately before administration of oral neomycin; follow-up enemas may be needed to completely empty bowel.
Topical therapy
• Don’t apply to more than 20% of body surface.
• Don’t apply to any body surface of patient with decreased renal function without considering risk-to-benefit ratio.
Otic therapy
• Reculture persistent drainage.
• Drug is best used in combination with other antibiotics.
• Avoid touching ear with dropper.

Patient education
• Instruct patient to report adverse reactions promptly.
• Encourage adequate fluid intake.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use