Polyene Antifungal Drugs

Drugs included in this group—amphotericin B, nystatin, natamycin, are used for treating systemic and superficial infections. Natamycin is used only for ophthalmologic superficial infection purposes.

Amphotericin B: Amphotericin B, [1R(1R*,3S*,5R*,6R*,9R*,11R*,15S*,16R*,17R*, 18S*,19E*,21E*,23*,25E*,27E*,29E*,31E*,33R*,35S*,36R*,37S*)]-33-[3-amino-3,6-dideoxy-Ăź-D-mannopyranosyl)-oxy]-1,3,5,6,9,11,17,37-octahydroxy-15,16,18-trimethyl-13-oxo-14,39-dioxabicyclo [33.3.1]nonatraconta-19,21,23,25,27,29,31-hepten-36-carbox ylic acid (35.1.1), is a large polyene antibiotic made from the cultural fluid of the actino-mycete Streptomyces nodosus [1-5].

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This compound has a broad spectrum of antifungal activity, including Candida albicans, Leishmania brasiliensis, Mycobacterium leprae, Histoplasma capsulatum, Blastomyces dermatitidus, and Coccidioides immitis. It possesses fungistatic and fungicidal activity depending on the dose used. The antifungal activity of amphotericin B is exhibited because it binds with sterols, in particular with ergosterol in the cellular membrane of sensitive fungi. This reaction makes pores in the membrane and increases the permeability of the membrane to small molecules, thus reducing the function of the membrane as an osmotic barrier and making the cells more sensitive to being destroyed. Amphotericin B is active against growing cells and cells that are dormant. However, this compound is not highly selective and reacts with host mammalian cells. Despite the many side effects, amphotericin B remains the primary drug for treating severe, acute systemic fungal infections. It is used for generalized fungal infections, such as can-didomycosis, aspergillosis, histoplasmosis, cryptococcosis, coccidioidomycosis, blasto-mycosis, and pulmonary mycoses. Synonyms of this drug are amphocyclin, fungisone, fungilin, and others.

Nystatin: Nystatin is stereoisomeric 33-[(3-amino-3,6-dideoxy-P-D-mannopyranosyl) oxy]-1,3,4,7,9,11,17,37-octahydroxy-15,16,18-trimethyl-13-oxo-14,39-dioxabicyclo [33.3.1] nonatriaconta-19,21,25,27,29,31-hexaen-36-carboxylic acid (35.1.2) [6-14].

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Nystatin was isolated in 1949 from the products of the vital activity of the actinomycete Streptomyces noursei, and it was the first antifungal antibiotic to be discovered. This polyene antibiotic is structurally similar to amphotericin B. It has a broad spectrum of activity. The mechanism of antifungal activity is similar to the mechanism of action of ampho-tericin B. It is used for preventing and treating candida infections of the skin and mucous membranes. In terms of preventative action, it is used for preventing the development of candidomycosis during prolonged treatment with penicillin drugs and antibiotics of other group, especially during oral use of tetracycline antibiotics, levomecytin, and others. Synonyms of this drug are biofanal, moronal, nicporil, fazigin, candex, and others.

Natamycin: Natamycin, a mixture of stereoisomeric 22-[(3-amino-3,6-dideoxy-0-D-mannopyranosyl)oxy]-1,3,26-trihydroxy-12-methyl-10-oxo-6,11,28-trioxatricy-clo[22.3.1.0.57]-octacosa-8,14,16,18,20,penten-25-carboxylic acid (35.1.3), like amphotericin and nystatin, is a polyene antibiotic that is isolated from the products of the vital activity of the actinomycete Streptomyces natalensis [15-17].

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