A yeast infection, or candidiasis, occurs when there is an overgrowth of a specific type of yeast called Candida. This common fungal infection can affect various parts of the body, including the skin, mouth, and vagina.
The Fungal Culprit: Candida
Candida is a type of yeast naturally present in and on the human body. The most common species responsible for infections is Candida albicans, typically found in small amounts on the skin, in the mouth, and within the digestive and vaginal tracts. Healthy bacteria usually maintain a balanced environment, preventing Candida from multiplying excessively. However, certain factors can disrupt this delicate balance, leading to an overgrowth of Candida and consequently, a yeast infection. Such factors include antibiotic use, which can eliminate beneficial bacteria, hormonal changes, or a weakened immune system.
Antifungal Strategies: How Medicines Work
Antifungal medications target specific components or processes within fungal cells that are not present in human cells, allowing selective action. A primary strategy involves disrupting the fungal cell membrane, a protective outer layer. Fungal cell membranes contain a unique sterol called ergosterol, which is functionally similar to cholesterol in human cells. Many antifungal drugs work by either interfering with the synthesis of ergosterol or by directly binding to it.
One common mechanism is the inhibition of ergosterol synthesis. Medications achieve this by blocking an enzyme crucial for ergosterol production, specifically 14-alpha-demethylase. When this enzyme is inhibited, ergosterol levels decline, compromising the membrane’s integrity, leading to leakage of the cell’s internal contents and ultimately causing cell death.
Another strategy involves directly binding to the ergosterol already present in the fungal cell membrane. This binding creates pores or channels in the membrane. These channels allow essential ions and molecules to leak out of the fungal cell, disrupting its internal balance and leading to its death. Because human cells utilize cholesterol instead of ergosterol, these medications primarily affect fungal cells, limiting harm to the host.
Common Antifungal Medications
Common antifungal medications for yeast infections fall into categories based on their mechanism. Azole antifungals, such as fluconazole, miconazole, and clotrimazole, are widely used. These medications inhibit the fungal enzyme 14-alpha-demethylase, disrupting the membrane’s structure and function. Fluconazole is typically available as an oral pill, often as a single dose, while miconazole and clotrimazole are commonly found in topical forms like creams or vaginal suppositories.
Polyene antifungals, with nystatin being a prominent example, represent another class of medications. Nystatin acts by directly binding to ergosterol in the fungal cell membrane. This binding creates holes in the membrane, causing the leakage of essential cellular components and leading to fungal cell death. Nystatin is often used for localized infections and is available in various forms, including oral suspensions for mouth infections and topical creams or vaginal tablets for skin and vaginal candidiasis.