An antifungal medication is a 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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Apart from side-effects like liver-damage or affecting estrogen levels, many anti-fungal medicines can cause allergic reactions in people. For example, the azole group of drugs is known to have caused anaphylaxis.
There are also many drug interactions. Patients must read in detail the enclosed data sheet(s) of the medicine. For example, the azole antifungals such as ketoconazole or itraconazole can be both substrates and inhibitors of the P-glycoprotein, which (among other functions) excretes toxins and drugs into the intestines.[1] Azole antifungals also are both substrates and inhibitors of the cytochrome P450 family CYP3A4,[1] causing increased concentration when administering, for example, calcium channel blockers, immunosuppressants, chemotherapeutic drugs, benzodiazepines, tricyclic antidepressants, macrolides and SSRIs.
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 including monovalent ions (K+, Na+, H+, and Cl-), small organic molecules leak and this is regarded one of the primary ways cell dies.[2] Animal cells contain cholesterol instead of ergosterol and so they are much less susceptible. However, at therapeutic doses, some amphotericin B may bind to animal membrane cholesterol, increasing the risk of human toxicity. Amphotericin B is nephrotoxic when given intravenously. 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.
Azole antifungal drugs inhibit the enzyme lanosterol 14 α-demethylase; the enzyme necessary to convert lanosterol to ergosterol. Depletion of ergosterol in fungal membrane disrupts the structure and many functions of fungal membrane leading to inhibition of fungal growth.[3]
Allylamines inhibit squalene epoxidase, another enzyme required for ergosterol synthesis:
Echinocandins may be used for systemic fungal infections in immunocompromised patients, they inhibit the synthesis of glucan in the cell wall via the enzyme 1,3-β glucan synthase:
Echinocandins are poorly absorbed when administered orally. When administered by injection they will reach most tissues and organs with concentrations sufficient to treat localized and systemic fungal infections.[4]
Research conducted in 1996 indicated that the following substances or essential oils had anti-fungal properties:[10]
Horopito (Pseudowintera colorata) leaf contains the anti-fungal compound polygodial.[8]
Israeli researchers at Tel Aviv University's Department of Plant Sciences published a study in 2009 indicating that carnivorous plants like the Venus flytrap contain compounds that may be useful in providing a new class of anti-fungal drugs for use in humans, for fungal infections that are resistant to current anti-fungal drugs.[11][12][13]
Antifungals work by exploiting differences between mammalian and fungal cells to kill 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 makes it more difficult to find or design drugs that target fungi without affecting human cells. As a consequence, many antifungal drugs cause side-effects. Some of these side-effects can be life-threatening if the drugs are not used properly.
Antifungal agents (such as ketoconazole) are often found in anti-dandruff shampoos. The antifungal drugs inhibit the yeast Malassezia globosa which encourages seborrhoeic dermatitis and tinea versicolor.
| Agent | Trade names | Medical applications |
| Ketoconazole[14] | Nizoral, Fungoral and Sebizole | Preliminary findings, research and studies including the completion of a small controlled clinical trial have produced data suggesting that ketoconazole shampoo is effective as a hair loss treatment in men with androgenic alopecia. Larger controlled clinical studies are still needed to evaluate the ideal dosage, formulation, and to determine the routine of treatment for this condition, thus ketoconazole shampoo is not FDA approved for this indication.[15] |
| Ciclopirox olamine | Loprox | The cream and lotion form of this agent is used to treat fungal infections of the skin. The lacquer form is used as part of a treatment plan to treat fungal infections of the nails. The shampoo form of this medication is used to treat and prevent dandruff or to treat seborrhoeic dermatitis. |
| Piroctone olamine | Octopirox[16] and Nivea Complete Control[17] | Piroctone olamine is sometimes used as an anti fungal agent, and it often used in dandruff shampoos in lieu of zinc. Piroctone Olamine is said to be less toxic than other anti-dandruff agents, often bypassing some of the normal FDA warnings, but still must be used with care, and only externally. |
| Zinc pyrithione[18] | Head & Shoulders, Johnson and Johnson ZP-11, Clinic All Clear, Pantene Pro V and Sikkai Powder | An antifungal and antibacterial agent first reported in the 1930s. Zinc pyrithione is best known for its use in the treatment of dandruff and seborrhoeic dermatitis. It also has antibacterial properties and is effective against many pathogens from the streptococcus and staphylococcus class. Its other medical applications include treatments of psoriasis, eczema, ringworm, fungus, athletes foot, dry skin, atopic dermatitis, tinea, and vitiligo. |
| Selenium sulfide | Selsun Blue, Head & Shoulders and Vichy Dercos Anti-Dandruff Shampoo | Selenium sulfide is available as a 1% and 2.5% lotion and shampoo. In some countries, the higher strength preparations requires a doctors prescription. The shampoo is used to treat dandruff and seborrhea of the scalp, and the lotion is used to treat tinea versicolor, a fungal infection of the skin. |
| Tar[19] | Neutrogena T-Gel | Is effective as a therapeutic treatment to control scalp itching and flaking symptomatic of scalp psoriasis, eczema, seborrhoeic dermatitis and dandruff. |
| Tea tree oil[20] | Dr. Bronner's Castile Soap | Is used topically as an ingredient in creams, ointments, lotions, soaps, and shampoos. In addition to antifungal properties, tea tree oil has antiseptic, antibacterial, and antiviral actions. It is effective against bacteria, viruses, fungal infections, mites (such as scabies), and lice (such as head lice). |
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