Neomycin selective toxicity

Neomycin is too toxic for parenteral use. Its only use is via the oral route for pre-operative sterilization of the bowel or for selective decontamination in hematologic patients. However absorption may be increased significantly if there is inflammation of the bowel wall and such absorption can pose problems for the patient. 

Topical uses. Neomycin and framycetin, whilst too toxic for systemic use, are effective for topical treatment of infections of the conjunctiva or external ear. They are sometimes used in antimicrobial combinations selectively to decontaminate the bowel of patients who are to receive intense immunosuppressive therapy. Tobramycin is given by inhalation for therapy of infective exacerbations of cystic fibrosis. 

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