Antimycotic, or antifungal, drugs are used to treat fungal infections. The major antifungal drug groups include:
• polyenes
• fluorinated pyrimidine
• imidazole
• synthetic triazoles
• glucan synthesis inhibitors
• synthetic allylamine derivatives.
The polyenes include amphotericin B and nystatin. Amphotericin B’s potency has made it the most widely used antimycotic drug for severe systemic fungal infections. It’s available in several forms, including lipid-based preparations that may decrease renal or systemic toxicity. Nystatin is used only topically or orally to treat local fungal infections because it’s extremely toxic when administered parenterally.
Pharmacokinetics
After I.V. administration, amphotericin B is distributed throughout the body and excreted by the kidneys. Its metabolism isn’t well defined. Oral nystatin undergoes little or no absorption, distribution, or metabolism. It’s excreted unchanged in stool. Topical nystatin isn’t absorbed through the skin or mucous membranes.
Pharmacodynamics
Amphotericin B works by binding to sterol (a lipid) in the fungal cell membrane, altering cell permeability (ability to allow a substance to pass through) and allowing intracellular components to leak out.
A license to kill
Amphotericin B usually acts as a fungistatic drug (inhibiting fungal growth and multiplication), but can become fungicidal (destroying fungi) if it reaches high concentrations in the fungi. Nystatin binds to sterols in fungal cell membranes and alters the permeability of the membranes, leading to loss of cell components. Nystatin can act as a fungicidal or fungistatic drug, depending on the organism present.
本期ISPN Review答案： 1. B. Gram negative bacteria only
Aminoglycoside antibiotics are used to treat Gram negative bacteria. They have not been shown to be effective against Gram positive bacteria and are not antifungal. Recall the major difference between the Gram negative and positive bacteria are their cell wall composition; Gram negative have a small proportion of peptidoglycan and a high proportion of lipopolysaccharide, while Gram negative bacteria have a large proportion of peptidoglycan.
2. D. Flucytosine
All of the drugs are antifungal agents but only flucytosine has been associated with bone marrow suppression and synergizes with other drugs which suppress bone marrow functions. Miconazole and ketoconazole may produce hepatotoxicity, gastro-intestinal upset and headaches. Amphotericin B may produce nephrotoxicity while itraconazole is associated with gastro-intestinal upset and rare liver dysfunction.
当前位置：
