Neomycin is an aminoglycoside antibiotic.
Administration
Neomycin sulfate is usually administered orally. In patients with hepatic encephalopathy who are unable to take oral medication, the drug has also been given as a retention enema.
Dosage
While potency of neomycin sulfate has been expressed both in terms of the base and the salt, dosage generally has been expressed in terms of the sulfate.
Dosages that follow are in terms of neomycin sulfate.
Hepatic Encephalopathy
As an adjunct in the treatment of hepatic encephalopathy, the usual adult oral dosage is 4-12 g of neomycin sulfate daily in 4 divided doses for 5-6 days. Patients with chronic hepatic insufficiency may require up to 4 g daily for an indefinite period.
Preoperative Intestinal Antisepsis
For preoperative intestinal antisepsis in patients undergoing colorectal surgery, oral neomycin sulfate is usually given for 24 hours, and treatment should not exceed 72 hours. A low residue diet should be prescribed. A saline cathartic should be administered (unless otherwise contraindicated) immediately preceding initiation of neomycin sulfate therapy. For the 24-hour regimen, the usual adult oral dosage of neomycin sulfate is 1 g each hour for 4 doses, then 1 g every 4 hours for the balance of the 24 hours. For the 2- to 3-day regimen, the usual daily dosage for adults and children is 88 mg/kg in 6 equally divided doses at 4-hour intervals. Alternatively, some clinicians recommend that if surgery is scheduled for 8 a.m., 1 g of neomycin sulfate and 1 g of erythromycin base should be administered at 1 p.m., 2 p.m., and 11 p.m. on the day preceding surgery as an adjunct to mechanical cleansing of the intestine.
Diarrhea Caused by Enteropathogenic E. coli
For the treatment of diarrhea caused by enteropathogenic E. coli, the usual oral dosage is 50 mg/kg daily in 4 divided doses for 2-3 days. In adults, a dosage of 3 g daily is usually adequate.
Urinary Tract Infections
Although most infectious disease experts no longer recommend parenteral use of neomycin, adults have been given 15 mg/kg daily administered in 4 equally divided IM doses every 6 hours in the treatment of urinary tract infections caused by susceptible organisms. However, a parenteral dosage form of the drug is no longer commercially available in the U.S.
Other Uses
For the treatment of hypercholesterolemia in adults, oral neomycin sulfate dosages of 500 mg to 2 g daily, administered in 2 or 3 divided doses with or immediately after meals, have been used.
Dosage should not exceed 2 g daily.
Dosage in Renal Impairment
Patients with renal impairment should receive reduced dosages of neomycin sulfate.
Pharmacokinetics
Absorption
Approximately 3% of an oral dose of neomycin sulfate is absorbed from the normal GI tract; however, impaired GI motility may increase absorption of the drug.
In a limited clinical study in adults, absorption of neomycin from retention enemas was similar to that following oral administration. In one study in adults with normal renal function, a single 4-g oral dose of neomycin sulfate produced peak plasma neomycin concentrations of 2.5-6. mcg/mL 1-4 hours after the dose in most patients; low plasma concentrations of the drug were detectable at 8 hours and no drug was detectable at 24 hours.
After IM administration of 300 mg of neomycin sulfate every 6 hours for 4 doses followed by 300 mg every 12 hours in adults, serum neomycin concentrations range from 12-30 mcg/mL 48-72 hours after the initial dose.
Elimination
The plasma elimination half-life of neomycin is usually 2-3 hours in adults with normal renal function and has been reported to be 12-24 hours in adults with impaired renal function. Following oral administration in adults, unabsorbed neomycin is excreted unchanged in the feces and approximately 1% of the dose is excreted in the urine by glomerular filtration within 24 hours.
Chemistry and Stability
Chemistry
Neomycin, an aminoglycoside antibiotic obtained from cultures of Streptomyces fradiae, is a complex of 3 components with various degrees of antimicrobial activity—neamine, neomycin B, and neomycin C.
The commercially available drug is comprised almost entirely of the sulfate salt of neomycin B and occurs as a white to slightly yellow, hygroscopic powder or cryodesiccated solid and is freely soluble in water and very slightly soluble in alcohol.
Neomycin sulfate oral solutions have a pH of 5-7.5. Although USP states that potency of neomycin sulfate should be expressed in terms of the base, potency and dosage generally have been expressed in terms of the sulfate. Each 500 mg of neomycin sulfate is approximately equivalent to 350 mg of neomycin.
Stability
Neomycin sulfate oral solution should be stored in tight, light-resistant containers, preferably at 15-30°C. Neomycin sulfate tablets should be stored in tight containers at 15-30°C. For further information on chemistry and stability, mechanism of action, spectrum, resistance, pharmacokinetics, uses, cautions, drug interactions, and dosage and administration of neomycin, see the Aminoglycosides General Statement 8:12.02. For topical uses of neomycin, see Neomycin 52:04.04 and 84:04.04.
Preparations
Neomycin Sulfate Powder Neo-Rx® Powder, Pharma- Tek Oral Solution 125 mg (87. mg of neomycin) Neo-Fradin®, Pharma- per 5 mL Tek Tablets 500 mg (350 mg of neomycin)