As with other antibiotics, use of oral neomycin may result in overgrowth of nonsusceptible organisms, particularly fungi. If this occurs, appropriate therapy should be instituted.
Neomycin is quickly and almost totally absorbed from body surfaces (except the urinary bladder) after local irrigation and when applied topically in association with surgical procedures. Delayed-onset irreversible deafness, renal failure and death due to neuromuscular blockade (regardless of the status of renal function) have been reported following irrigation of both small and large surgical fields with minute quantities of neomycin.
Cross-allergenicity among aminoglycosides has been demonstrated.
Aminoglycosides should be used with caution in patients with muscular disorders such as myasthenia gravis or parkinsonism since these drugs may aggravate muscle weakness because of their potential curare-like effect on the neuromuscular junction.
Small amounts of orally administered neomycin are absorbed through intact intestinal mucosa.
There have been many reports in the literature of nephrotoxicity and/or ototoxicity with the oral use of neomycin. If renal insufficiency develops during oral therapy, consideration should be given to reducing the drug dosage or discontinuing therapy.
An oral neomycin dose of 12 grams per day produces a malabsorption syndrome for a variety of substances, including fat, nitrogen, cholesterol, carotene, glucose, xylose, lactose, sodium, calcium, cyanocobalamin and iron.
Orally administered neomycin increases fecal bile acid excretion and reduces intestinal lactase activity.
Patients with renal insufficiency may develop toxic neomycin blood levels unless doses are properly regulated. If renal insufficiency develops during treatment, the dosage should be reduced or the antibiotic discontinued. To avoid nephrotoxicity and eighth nerve damage associated with high doses and prolonged treatment, the follow ing should be performed prior to and periodically during therapy: urinalysis for increased excretion of protein, decreased specific gravity, casts and cells; renal function tests such as serum creatinine, BUN or creatinine clearance; tests of the vestibulocochlearis nerve (eighth cranial nerve) function.
Serial, vestibular and audiometric tests should be performed (especially in high-risk patients). Since elderly patients may have reduced renal function which may not be evident in the results of routine screening tests such as BUN or serum creatinine, a creatinine clearance determination may be more useful.
Carcinogenesis, Mutagenesis, Impairment of Fertility
No long-term animal studies have been performed with neomycin sulfate to evaluate carcinogenic or mutagenic potential or impairment of fertility.
Category D: (See WARNINGS section.)
It is not known whether neomycin is excreted in human milk, but it has been shown to be excreted in cow milk following a single intramuscular injection. Other aminoglycosides have been shown to be excreted in human milk. Because of the potential for serious adverse reactions from the aminoglycosides in nursing infants, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
The safety and efficacy of oral neomycin sulfate in patients less than 18 years of age have not been established. If treatment of a patient less than 18 years of age is necessary, neomycin should be used with caution and the period of treatment should not exceed two weeks because of absorption from the gastrointestinal tract.