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Antifungal drug
From Wikipedia, the free encyclopedia
An antifungal drug is medication used to treat fungal infections such as athlete's foot, ringworm, candidiasis (thrush), serious systemic infections such as cryptococcal meningitis, and others. Such drugs are usually obtained by a doctor's prescription or purchased over-the-counter.
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Antifungals work by exploiting differences between mammalian and fungal cells to kill off the fungal organism without dangerous effects on the host. Unlike bacteria, both fungi and humans are eukaryotes. Thus fungal and human cells are similar at the molecular level. This means it is more difficult to find a target for an antifungal drug to attack that does not also exist in the infected organism. Consequently, there are often side-effects to some of these drugs. Some of these side-effects can be life-threatening if not used properly.
There are several classes of antifungal drugs.
A polyene is a circular molecule consisting of a hydrophobic and hydrophilic region. This makes polyene an amphoteric molecule. The polyene antimycotics bind with sterols in the fungal cell membrane, principally ergosterol. This changes the transition temperature (Tg) of the cell membrane, thereby placing the membrane in a less fluid, more crystalline state. As a result, the cell's contents leak out (usually the hydrophilic contents) and the cell dies. Animal cells contain cholesterol instead of ergosterol and so they are much less susceptible. (Note: as polyene's hydrophobic chain is reduced, its sterol binding activity is increased. Therefore, increased reduction of the hydrophobic chain may result in it binding to cholesterol, making it toxic to animals.)
- Natamycin -- 33 Carbons, binds well to ergosterol
- Rimocidin
- Filipin -- 35 Carbons, binds to cholesterol (toxic)
- Nystatin
- Amphotericin B
The imidazole and triazole antifungal drugs inhibit the enzyme cytochrome P450 14α-demethylase. This enzyme converts lanosterol to ergosterol, and is required in fungal cell membrane synthesis. These drugs also block steroid synthesis in humans.
- Miconazole (Miconazole nitrate)
- Ketoconazole
- Clotrimazole - marketed as Lotrimin or Lotrimin AF (and Canesten in the UK)
- Econazole
- Bifonazole
- Butoconazole
- Fenticonazole
- Isoconazole
- Oxiconazole
- Sertaconazole - marketed as Ertaczo in North America
- Sulconazole
- Tioconazole
The triazoles are newer, and are less toxic[citation needed] and more effective[citation needed]:
Allylamines inhibit the enzyme squalene epoxidase, another enzyme required for ergosterol synthesis:
- Terbinafine - marketed as "Lamisil" in North America, Australia and the UK
- Amorolfine
- Naftifine - marketed as "Naftin" in North America
- Butenafine - marketed as Lotrimin Ultra
Echinocandins inhibit the synthesis of glucan in the cell wall, probably via the enzyme 1,3-β glucan synthase:
Others:
- Ciclopirox is a fungicidal. Its real name is ciclopirox olamine.
- Flucytosine, or 5-fluorocytosine, is an antimetabolite.
- Griseofulvin binds to polymerized microtubules and inhibits fungal mitosis.
- Gentian Violet
- Haloprogin
- Tolnaftate is fungicidal, marketed as Tinactin, Desenex, Aftate, as well as other names
- Undecylenic acid is fungistatic
Alternatives:[1]
- Tea tree oil -- ISO 4730 ("Oil of Melaleuca, Terpinen-4-ol type")
- Citronella oil
- lemon grass
- orange oil
- palmarosa oil
- patchouli
- lemon myrtle
- Neem Seed Oil
- Coconut Oil -- medium chain triglycerides in the oil have antifungal activities
- Zinc dietary supplements or natural food sources, including pumpkin seeds and chick peas
- Selenium dietary supplements or natural food sources, particularly Brazil nuts
Antifungal drugs are often found in dandruff shampoos. Among the most common are pyrithione zinc,selenium sulphide and ketoconazole (Nizoral).
- ^ Pattnaik S, Subramanyam VR, Kole C (1996). "Antibacterial and antifungal activity of ten essential oils in vitro". Microbios 86 (349): 237-46. PMID 8893526.
- Antifungal Drugs - Detailed information on antifungals from the Fungal Guide written by Drs. R. Thomas and K. Barber
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| Antibiotics | Griseofulvin • polyene antimycotics (Natamycin, Nystatin) |
| Topical azoles | imidazoles (Bifonazole, Clomidazole, Clotrimazole, Econazole, Fenticonazole, Ketoconazole, Isoconazole, Miconazole, Oxiconazole, Sertaconazole, Sulconazole, Tioconazole) • triazoles (Fluconazole) • benzimidazole (Thiabendazole) |
| Other topicals | Ciclopirox • Ethylparaben • Flucytosine • Salicylic acid • Selenium sulfide • Tolnaftate • Undecylenic acid • allylamines (Amorolfine, Butenafine, Naftifine, Terbinafine) |
| For systemic use | Griseofulvin • allylamine (Terbinafine) • polyene antimycotic (Amphotericin B) • triazoles (Itraconazole, Posaconazole, Voriconazole) • echinocandins (Anidulafungin, Caspofungin, Micafungin) |
| Other | Tea tree oil • citronella oil • lemon grass • orange oil • patchouli • lemon myrtle |