Neomycin¿¡ ´ëÇÑ Mechanism_Of_Action Á¤º¸ Aminoglycosides like neomycin "irreversibly" bind to specific 30S-subunit proteins and 16S rRNA. Specifically neomycin binds to four nucleotides of 16S rRNA and a single amino acid of protein S12. This interferes with decoding site in the vicinity of nucleotide 1400 in 16S rRNA of 30S subunit. This region interacts with the wobble base in the anticodon of tRNA. This leads to interference with the initiation complex, misreading of mRNA so incorrect amino acids are inserted into the polypeptide leading to nonfunctional or toxic peptides and the breakup of polysomes into nonfunctional monosomes. Nystatin¿¡ ´ëÇÑ Mechanism_Of_Action Á¤º¸ Nystatin interacts with 14-¥á demethylase, a cytochrome P-450 enzyme necessary for the conversion of lanosterol to ergosterol. This results in inhibition of ergosterol synthesis and increased fungal cellular permeability.
Pharmacology
Neomycin¿¡ ´ëÇÑ Pharmacology Á¤º¸ Neomycin is an aminoglycoside antibiotic. Aminoglycosides work by binding to the bacterial 30S ribosomal subunit, causing misreading of t-RNA, leaving the bacterium unable to synthesize proteins vital to its growth. Aminoglycosides are useful primarily in infections involving aerobic, Gram-negative bacteria, such as Pseudomonas, Acinetobacter, and Enterobacter. In addition, some mycobacteria, including the bacteria that cause tuberculosis, are susceptible to aminoglycosides. Infections caused by Gram-positive bacteria can also be treated with aminoglycosides, but other types of antibiotics are more potent and less damaging to the host. In the past the aminoglycosides have been used in conjunction with penicillin-related antibiotics in streptococcal infections for their synergistic effects, particularly in endocarditis. Aminoglycosides are mostly ineffective against anaerobic bacteria, fungi and viruses. Nystatin¿¡ ´ëÇÑ Pharmacology Á¤º¸ Nystatin is an antibiotic which is both fungistatic and fungicidal in vitro against a wide variety of yeasts and yeast-like fungi, including Candida albicans, C. parapsilosis, C. tropicalis, C. guilliermondi, C. pseudotropicalis, C. krusei, Torulopsis glabrata, Tricophyton rubrum, T. mentagrophytes. Nystatin acts by binding to sterols in the cell membrane of susceptible species resulting in a change in membrane permeability and the subsequent leakage of intracellular components. On repeated subculturing with increasing levels of nystatin, Candida albicans does not develop resistance to nystatin. Generally, resistance to nystatin does not develop during therapy. However, other species of Candida (C. tropicalis, C. guilliermondi, C. krusei, and C. stellatoides) become quite resistant on treatment with nystatin and simultaneously become cross resistant to amphotericin as well. This resistance is lost when the antibiotic is removed. Nystatin exhibits no appreciable activity against bacteria, protozoa, or viruses.
Neomycin¿¡ ´ëÇÑ ´Ü¹é°áÇÕ Á¤º¸ Protein binding studies have shown that the degree of aminoglycoside protein binding is low and, depending upon the methods used for testing, may be between 0% and 30%.
Half-life
Neomycin¿¡ ´ëÇÑ ¹Ý°¨±â Á¤º¸ 2 to 3 hours Nystatin¿¡ ´ëÇÑ ¹Ý°¨±â Á¤º¸ Not Available
Absorption
Neomycin¿¡ ´ëÇÑ Absorption Á¤º¸ Poorly absorbed from the normal gastrointestinal tract. Although only approximately 3% of neomycin is absorbed through intact intestinal mucosa, significant amounts may be absorbed through ulcerated or denuded mucosa or if inflammation is present. Nystatin¿¡ ´ëÇÑ Absorption Á¤º¸ Nystatin is not absorbed from intact skin or mucous membrane
Neomycin¿¡ ´ëÇÑ Toxicity Á¤º¸ LD50 = 200 mg/kg (rat). Because of low absorption, it is unlikely that acute overdosage would occur with oral neomycin. However, prolonged administration could result in sufficient systemic drug levels to produce neurotoxicity, ototoxicity and/or nephrotoxicity. Nystatin¿¡ ´ëÇÑ Toxicity Á¤º¸ Not Available
Drug Interactions
Neomycin¿¡ ´ëÇÑ Drug_Interactions Á¤º¸ Not Available Nystatin¿¡ ´ëÇÑ Drug_Interactions Á¤º¸ Not Available
Neomycin¿¡ ´ëÇÑ Description Á¤º¸ A component of neomycin that is produced by Streptomyces fradiae. On hydrolysis it yields neamine and neobiosamine B. (From Merck Index, 11th ed) Nystatin¿¡ ´ëÇÑ Description Á¤º¸ Nystatin is a polyene antifungal drug to which many molds and yeasts are sensitive, including Candida spp. Nystatin has some toxicity associated with it when given intravenously, but it is not absorbed across intact skin or mucous membranes. It is considered a relatively safe drug for treating oral or gastrointestinal fungal infections.