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Antifungal drug
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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.
fungals work by exploiting differences between mammalian and fungal cells to kill off the fungal organism without dangerous effects on the host.
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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.
List of antifungal drugs
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 weakness in fungi to attack that does not also exist in human cells - so, if you attack the fungus, you may also attack the human cells the fungus lives on. 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.
Polyene antifungals
A polyene is a molecule with multiple conjugated double bonds. A polyene antifungal is a macrocyclic polyene with a heavily hydroxylated region on the ring opposite the conjugated system. This makes polyene antifungals amphiphilic. 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 a polyene's hydrophobic chain is shortened, its sterol binding activity is increased. Therefore, further reduction of the hydrophobic chain may result in it binding to cholesterol, making it toxic to animals.)
Imidazole and Triazole antifungals
The imidazole and triazole are synthetic antifungal drugs that inhibit the enzyme cytochrome P450 14a-demethylase. This enzyme converts lanosterol to ergosterol, and is required in fungal cell membrane synthesis.
These drugs also block steroid synthesis in humans.
Imidazoles:
The triazoles are newer, and are less toxic and more effective:
Triazoles:
Allylamines
Allylamines inhibit the enzyme squalene epoxidase, another enzyme required for ergosterol synthesis:
- Terbinafine - marketed as "Lamisil" in North America, Australia, the UK, Germany and the Netherlands.
- Amorolfine
- Naftifine - marketed as "Naftin" in North America.
- Butenafine - marketed as Lotrimin Ultra.
Echinocandins
Echinocandins inhibit the synthesis of glucan in the cell wall, probably via the enzyme 1,3-ß glucan synthase:
Others
- Haloprogin - discontinued due to the emergence of more modern antifungals with fewer side effects .
Alternatives
Anti-Dandruff shampoos
Antifungal drugs are often found in Anti-dandruff shampoos, the antifungal drugs inhibit the yeast, Malassezia furfur (formerly known as Pityrosporum ovale) which encourage seborrhoeic dermatitis and Tinea versicolor.
| Active ingredient | Example of product | Comments | | Sodium bicarbonate (baking soda) | Arm & Hammer | | | Ketoconazole | Nizoral, or Fungoral | There is a claim that Nizoral shampoo has hair loss benefits but Nizoral Shampoo does not have FDA approval as a hair loss remedy . | | Ciclopirox olamine | Loprox | Show similar efficacy to ketoconazole with a relative increase in subjective symptom relief due to its inherent anti-inflammatory properties. | | Piroctone olamine (Octopirox) | Nivea Complete Control | a replacement for the commonly used compound zinc pyrithione | | Zinc pyrithione | Head & Shoulders, Johnson and Johnson ZP-11, Clinic All Clear, Pantene Pro V, Sikkai Powder | An antifungal and antibacterial agent, was first reported in the 1930s. | | Selenium sulfide | Selsun Blue, Vichy Dercos Anti-Dandruff shampoo, other varieties of Head & Shoulders | In USA, 1% strength is available over-the-counter, and a 2.5% strength is also available with a prescription | | Tar | Neutrogena T/Gel | | | Tea tree oil | | |
See also
External links
- - Detailed information on antifungals from the Fungal Guide written by Drs. R. Thomas and K. Barber
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