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Neo-Fradin (Neomycin Sulfate) - Description and Clinical Pharmacology


To reduce the development of drug-resistant bacteria and maintain the effectiveness of Neomycin Sulfate Oral Solution and other antibacterial drugs, Neomycin Sulfate Oral Solution should be used only to treat or prevent infections that are proven or strongly suspected to be caused by bacteria.


NEO-FRADIN Oral Solution for oral administration contains neomycin which is an antibiotic obtained from the metabolic products of the actinomycete Streptomyces fradiae. The pH range is 5.0 to 7.5. NEO-FRADIN Oral Solution is a clear orange solution with a cherry flavor. Each 5 mL of NEO-FRADIN Oral Solution contains 125 mg of neomycin sulfate (equivalent to 87.5 mg of neomycin).

Inactive ingredients: benzoic acid, FD&C yellow no. 6, cherry flavor, glycerin, methylparaben, proplyparaben, sodium phosphate dibasic heptahydrate, sulfuric acid, and purified water.

Sodium phosphate dibasic heptahydrate and sulfuric acid are used as pH adjusters.

The chemical name for Neomycin is: 0-2, 6-diamino-2, 6-dideoxy-α-D-lucopyranosyl-(1→3)- 0β-D-ribofuranosyl-(1→5)0-[2, 6-diamino-2, 6-dideoxy-α-D-glucopyranosyl-(1→4)]-2-deoxy-D-streptamine.

Neomycin B is identical except that the -α-D-glucopyranosyl residue in the neobiosamine moiety is β-L-idopyranosly.

The molecular weight of Neomycin is 614.67. The structural formula is represented below:

neomycin molecular structure

neomycin molecular structure


Neomycin sulfate is poorly absorbed from the gastrointestinal tract. The small absorbed fraction is rapidly distributed in the tissues and is excreted by the kidney in keeping with the degree of kidney function. The unabsorbed portion of the drug (approximately 97 percent) is eliminated unchanged in the feces.

Growth of most intestinal bacteria is rapidly suppressed following oral administration of neomycin sulfate, with the suppression persisting for 48 to 72 hours. Nonpathogenic yeasts and occasionally resistant strains of Enterobacter aerogenes (formerly Aerobacter aerogenes) replace the intestinal bacteria.

As with other aminoglycosides, the amount of systemically absorbed neomycin transferred to the tissues increases cumulatively with each repeated dose administered until a steady state is achieved. The kidney functions as the primary excretory path as well as the tissue binding site with the highest concentration found in renal cortex. With repeated dosings, progressive accumulation also occurs in the inner ear. Release of tissue bound neomycin occurs slowly over a period of several weeks after dosing has been discontinued.

Protein binding studies have shown that the degree of aminoglycoside protein binding is low and, depending upon the methods used for testing, this may be between 0 and 30 percent.


In vitro tests have demonstrated that neomycin is bactericidal and acts by inhibiting the synthesis of protein in susceptible bacterial cells. It is effective primarily against gram-negative bacilli but does have some activity against gram-positive organisms. Neomycin is active in vitro against Escherichia coli and the Klebsiella-Enterobacter group. Neomycin is not active against anaerobic bowel flora.

If susceptibility testing is needed, using a 30 mcg disc, organisms producing zones of 16 mm or greater are considered susceptible. Resistant organisms produce zones of 13 mm or less. Zones greater than 13 mm and less than 16 mm indicate intermediate susceptibility.

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