Antibiotic agents neomycin

Uses topical antibiotic agent, often used in combination with neomycin products include ointments, creams, eye, and ear drops Cross bacitracin. Important allergen in leg ulcer dermatitis... 

A Acetylation, O-Phosphorylation, and O-Adenylylation. A/-Acetylation, O-phosphorjiation, and O-adenyljiation provide mechanisms by which therapeutically valuable aminocyclitol antibiotics, eg, kanamycia [8063-07-8] gentamicin [1403-66-3] sisomicin [32385-11-8], streptomycia [57-92-1], neomycin, or spectinomycin are rendered either partially or completely iaactive. Thus, eg, kanamycia B [4696-78-8] (50) can be iaactivated by modification at several sites, as shown. The elucidation of these mechanisms has allowed chemical modification of the sites at which the iaactivation occurs. Several such bioactive analogues, eg, dibekacia and amikacin have been prepared and are not subject to the iaactivation hence, they inhibit those organisms against which the parent antibiotics are iaeffective (96) (see Antibacterial agents, synthetic). 

Nystatin (100,000 lU) is also available in combination with neomycin sulfate [1405-10-3] (35,000 lU), polymyxin B sulfate [1405-20-5] (35,000 lU), acetarsol [97-44-9] (150 mg), and dimethicone [8050-81-5] (2,500 mg). One or two ovules per day are inserted vaginaHy for at least 6—12 days. This combination has an antibacterial, antimycotic, and antitrichomonas action (see also Antibiotics, oligosaccharides Antiparasitic agents, antiprotozoals). 

Intravenous antibiotic administration is the most common delivery method for surgical prophylaxis. Intravenous administration ensures complete bioavailability while minimizing the impact of patient-specific variables. Oral administration is also used in some bowel operations. Non-absorbable compounds like erythromycin base and neomycin are given up to 24 hours prior to surgery to cleanse the bowel. Note that oral agents are used adjunctively and do not replace IV agents. 

Systemic therapy with a variety of (3-lactams, macro-lides and lincosamides (clindamycin) has been the cornerstone of skin infection therapy for many years [17]. However, topical antibiotics can play an important role in both treatment and prevention of many primary cutaneous bacterial infections commonly seen in the dermatological practice [18], Indeed, while systemic antimicrobials are needed in the complicated infections of skin and skin structure, the milder forms can be successfully treated with topical therapy alone [18], The topical agents used most often in the treatment of superficial cutaneous bacterial infections are tetracyclines, mupirocin, bacitracin, polymyxin B, and neomycin. 

Polymyxin B is effective against many gramnegative bacteria, including E. coli, Klebsiella, and Salmonella. Systemic administration of this drug, however, is often associated with extreme nephrotoxicity. Hence, this agent is used primarily for the treatment of local, superficial infections of the skin, eyes, and mucous membranes. When applied topically for these conditions, adverse reactions are relatively rare. Polymyxin B is often combined with other antibiotics such as bacitracin and neomycin in commercial topical preparations. 

Antibiotics such as neomycin, streptomycin, kanamycin, gentamycin, polymyxin A, polymyxin B, colistin, lincomycin, and tetracycline have all been implicated as augmenting the action of the nondepolarizing agents. 

It is well documented that antimicrobial agents cause cross-resistance. Use of antibiotics causes alterations in normal microbial flora of the body. The suprain-fection is a common problem associated with antibiotic therapy and is very difficult to treat. Prolonged uses of antibiotics alter the microflora of the intestine and cause vitamin deficiency. Neomycin causes morphologic abnormalities in the intestinal mucosa. 

Although topical antibiotics are used frequently in the management of ocular rosacea, no firm evidence demonstrates their efficacy as a sole therapeutic agent. Topical steroids, however, are effective for treating the inflammatory aspects and frequently are used four times daily in conjimction with antibiotics in combination products such asTobraDex (tobramycin-dexamethasone), Pred-G (gentamicin-prednisone), or Maxitrol (neomycin-polymyxin B-dexamethasone). Because of potential steroid-induced side effects, chronic use of these agents should be avoided. 

In rats, ototoxicity caused by gentamicin or tobramycin was amehorated by melatonin, which did not interfere with the antibiotic action of the aminoglycosides (70). The free radical scavenging agent alpha-lipoic acid has previously been shown to protect against the cochlear adverse effects of systemically administered aminoglycoside antibiotics, and in a recent animal study it also prevented cochlear toxicity after the administration of neomycin 5% directly to the round window membrane over 7 days (71). 

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. 

By early 2004, 15 million doses of smallpox vaccine, Dryvax, were available in the United States. Dryvax, a Wyeth product, is a live virus preparation of vaccinia. The vaccine comes as a lyophilized (freeze-dried) powder in 100 dose vials containing the antibiotics polymyxin B, streptomycin, tetracycline, and neomycin. Fifty percent glycerin, containing a small amount of phenol as a preservative, serves as the diluent for reconstitution (25). Studies have shown that diluting the vaccine in a 1 5 ratio could expand the supply without reducing vaccine efficacy (25). In addition, 200 million antibiotic-free doses are in production. The CDC Web site has detailed directions on how to reconstitute and administer the vaccine at http //www.bt.cdc.gov/agent/smallpox/vaccination/ administration.asp. 

A number of antibiotics have been used as aerosol therapies. Examples include beta lactam agents, polymycin antimicrobials, neomycin, gentamicin, and tobramycin. Many of the early efforts were reported as case studies, and observations and data regarding safety and efficacy were lacking. Controlled clinical trials were not conducted until the middle of the 1980s. More recent evaluations have focused on the role of inhaled tobramycin used as suppressive therapy for cystic fibrosis patients colonized with Pseudomonas aeruginosa. 

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