Hepatic encephalopathy neomycin

A combination of neomycin and nonabsorbable erythromycin base given orally prior to colorectal surgery can markedly reduce the incidence of postoperative wound infection. Orally administered neomycin is sometimes used to suppress the facultative flora of the gut in patients with hepatic encephalopathy. It is unclear how this improves coma, but one theory is that it reduces systemic absorption of the bacterial metabo-htes that allegedly cause hepatic encephalopathy. Although more than 95% of an oral dose of neomycin is excreted unchanged in the stool of normal subjects, the bioavaUabUity of neomycin may be much higher in patients with an abnormal gastrointestinal mucosa. 

Neomycin Oral or topical, poor bioavailability used before bowel surgery to decrease aerobic flora also used to treat hepatic encephalopathy... 

Suppression of bowel flora is thought by some to be useful in hepatic encephalopathy. Here, absorption of products of bacterial breakdown of protein (ammonium, amines) in the intestine lead to cerebral symptoms and even to coma. In acute coma, neomycin 6 g/d should be given by gastric tube as prophylaxis, 1-4 g/d may be given to patients with protein intolerance who fail to respond to dietary protein restriction (see also lactulose, p. 640). 

Long-term application of lactulose, possibly in shortterm combination with neomycin or paromomycin, is recommended. This is especially true when there are signs of an onset of hepatic encephalopathy. 

Neomycin is not usually administered parenter-ally to animals because of nephrotoxicity and ototoxicity. Only 3% of a dose of neomycin is absorbed following p.o. administration it is, therefore, used in the therapy of coliform enteritis in small and large animals. It is available as tablets, boluses and water additives, in many different combinations with antibiotics, corticosteroids and anticholinergic agents. It can also be used to decrease nitrogenous waste production by the normal gastrointestinal flora in animals with hepatic encephalopathy. Neomycin is not absorbed through the skin, so it is frequently utilized as the antibacterial constituent in ophthalmic formulations (especially in combination with bacitracin and polymyxin B) and in preparations for the treatment of otitis externa in small animals. 

Treatment is largely empirical, based on observations that intestinal bacteria and protein loads in the intestinal tract are important in the symptoms of hepatic encephalopathy. Lactulose has long been recognized to reduce the symptoms in chronic hepatic encephalopathy. Antibiotic treatment with a nonabsorbable antibiotic such as neomycin reduces the number of bacteria and is especially helpful in patients with GI bleeding. Protein reduction in the diet also improves encephalopathy reducing dietary protein to the less than 40g/day often needed to improve symptoms may compromise nutrition. Patients with acute encephalopathy require... 

Kanamycin can be administered orally as adjunctive therapy in cases of hepatic encephalopathy. The dose is 4 to 6 g/day for 36 to 72 hours quantities as large as 12 g/day (in divided doses) have been given. It is ototoxic and nephrotoxic. Like neomycin, its oral administration can cause malabsorption and superinfection. 

The oral administration of neomycin (usually in combination with erythromycin base) has been employed primarily for preparation of the bowel for surgery. For therapy of hepatic encephalopathy, a daily dose of 4 to 12 g (in divided doses) by mouth is given, provided that renal function is normal. Because renal insufficiency is a complication of hepatic failure and neomycin is nephrotoxic, it is used rarely for this indication. Lactulose is a much less toxic agent and is preferred. 

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