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Chapter: Essential pharmacology : Aminoglycoside Antibiotics

Obtained from S. fradiae , it is a widespectrum aminoglycoside, active against most gram-negative bacilli and some gram-positive cocci.



Obtained from S. fradiae , it is a widespectrum aminoglycoside, active against most gram-negative bacilli and some gram-positive cocci.

However, Pseudomonas and Strep. pyogenes are not sensitive. Neomycin is highly toxic to the internal ear (mainly auditory) and to kidney. It is, therefore, not used systemically. Absorption from the g.i.t. is minimal. Oral and topical administration does not ordinarily cause systemic toxicity.


Dose: 0.25–1 g QID oral, 0.3–0.5% topical.


NEOMYCIN SULPHATE 350, 500 mg tab, 0.3% skin oint, 0.5% skin cream, eye oint.


NEBASULF: Neomycin sulph. 5 mg, bacitracin 250 U, sulfacetamide 60 mg/g oint. and powder for surface application.


POLYBIOTIC CREAM: Neomycin sulph. 5 mg, polymyxin 5,000 IU, gramicidin 0.25 mg/g cream.


NEOSPORIN: Neomycin 3400 iu, polymyxin B 5000 iu, bacitracin 400 iu/g oint and powder for surface application. NEOSPORINH: Neomycin 3400 iu, polymyxin B 5000 iu, hydrocortisone 10 mg per g oint and per ml ear drops.




1. Topically (often in combination with polymyxin, bacitracin, etc.) for infected wound, ulcers, burn, external ear infections, conjunctivitis, but like other topical antiinfective preparations, benefits are limited.


2. Orally for:


a) Preparation of bowel before surgery: (3 doses of 1.0 g along with metronidazole 0.5 g on day before surgery) may reduce postoperative infections.

b) Hepatic coma: Normally NH3 is produced by colonic bacteria. This is absorbed and converted to urea by liver. In severe hepatic failure, detoxication of NH3 does not occur, blood NH3 levels rise and produce encephalopathy. Neomycin, by suppressing intestinal flora, diminishes NH3 production and lowers its blood level; clinical improvement is seen within 2–3 days. However, because of toxic potential it is infrequently used for this purpose; lactulose is preferred.


Adverse Effects


Applied topically neomycin has low sensitizing potential. However, rashes do occur.


Oral neomycin has a damaging effect on intestinal villi—prolonged treatment can induce malabsorption syndrome with diarrhoea and steatorrhoea. It can decrease the absorption of digoxin and many other drugs, as well as bile acids.


Due to marked suppression of gut flora, superinfection by Candida can occur.


Small amounts that are absorbed from the gut or topical sites are excreted unchanged by kidney. This may accumulate in patients with renal insufficiency—cause further kidney damage and ototoxicity. Neomycin is contraindicated if renal function is impaired.


Applied to serous cavities (peritoneum), it can cause apnoea due to muscle paralysing action. Neomycin containing anti-diarrhoeal formulations are banned in India.


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