Ketoconazole

Skin and Scalp Infections

Topical forms of ketoconazole, including creams and shampoos, are used to treat several types of fungal skin infections. These include:

• Tinea corporis: Commonly known as ringworm of the body.
• Tinea cruris: Often referred to as jock itch.
• Tinea pedis: Known as athlete's foot.
• Tinea versicolor: A fungal infection that causes small, discolored patches on the skin.
• Cutaneous candidiasis: Yeast infections that affect the skin.
• Seborrheic dermatitis: A condition that causes scaly patches, red skin, and stubborn dandruff on the scalp or other oily areas of the body.

Systemic Fungal Infections

Ketoconazole oral tablets are prescribed for serious fungal infections that affect the internal organs. Due to the risk of significant side effects, the oral form is generally reserved for situations where other antifungal therapies are not available or cannot be tolerated by the patient. Conditions treated with the oral form may include:

• Blastomycosis
• Coccidioidomycosis
• Histoplasmosis
• Chromomycosis
• Paracoccidioidomycosis

Oral ketoconazole is not recommended for the treatment of fungal infections of the fingernails or toenails, nor is it used for fungal meningitis.

Mechanism of Action

Ketoconazole belongs to a class of medications called azole antifungals. It works by interfering with the synthesis of ergosterol, which is a vital component of fungal cell membranes. Ergosterol is necessary for the fungus to maintain its structural integrity and function.

When ketoconazole blocks the production of ergosterol, the fungal cell membrane becomes damaged and more permeable. This disruption causes the internal contents of the fungal cell to leak out, which stops the fungus from growing or leads to its death. This process helps to clear the infection and prevent it from spreading to other parts of the body.

How It Targets Fungi

Ketoconazole is effective against a variety of fungi and yeasts. The way it is applied determines how it interacts with the body:

• Topical application: When used as a cream or shampoo, the medication works locally on the skin or scalp. It targets the fungi living on the surface or within the top layers of the skin without being absorbed significantly into the bloodstream.
• Oral administration: When taken as a tablet, the medication is absorbed into the system to treat serious fungal infections. Because of the risk of side effects, the oral form is generally reserved for cases where other antifungal treatments have failed or are not tolerated.

Common Side Effects

Side effects vary depending on whether ketoconazole is applied to the skin or taken as an oral tablet.

Topical Side Effects

• Skin itching, stinging, or burning
• Dry skin or redness
• Changes in hair texture or scalp oiliness
• Mild skin irritation

Oral Side Effects

• Nausea and vomiting
• Stomach pain
• Headache
• Dizziness

Serious Side Effects

Contact a healthcare provider immediately if you experience any of the following:

• Liver issues: Yellowing of the eyes or skin, dark urine, pale stools, or severe fatigue.
• Adrenal problems: Extreme tiredness, muscle weakness, or loss of appetite.
• Severe skin reactions: Blistering, oozing, or an intense rash.
• Allergic reactions: Swelling of the face or throat, severe dizziness, or trouble breathing.

Boxed Warnings for Oral Tablets

Oral ketoconazole tablets carry several boxed warnings due to the risk of severe and potentially fatal side effects:

• Liver Damage: Serious liver toxicity, including cases resulting in death or the need for a liver transplant, has occurred with oral use. This damage can occur even in patients with no prior history of liver disease. Monitoring of liver function is typically required before and during treatment.
• Heart Rhythm Issues: When taken with certain other medications, ketoconazole can cause QT prolongation, a serious heart rhythm condition that can lead to life-threatening arrhythmias.
• Drug Interactions: Many medications interact dangerously with oral ketoconazole. It is contraindicated for use with several drugs because it can cause those medications to reach toxic levels in the blood.

Adrenal Insufficiency

Oral ketoconazole can decrease the body's production of corticosteroids by the adrenal glands. This may lead to adrenal insufficiency, particularly when the body is under physical stress such as surgery, injury, or severe infection. Healthcare providers may monitor adrenal function in patients taking high doses.

Topical Precautions

Topical forms of ketoconazole, including creams, gels, and shampoos, are not absorbed into the bloodstream in significant amounts and do not carry the same systemic risks as oral tablets. However, precautions include:

• Skin Irritation: Some users may experience redness, itching, or burning at the application site.
• Allergic Reactions: Allergic contact dermatitis is possible. If a severe reaction occurs, use should be discontinued.
• Hair Changes: The shampoo form may cause changes in hair texture or color, or scalp irritation.

Contraindications

Oral ketoconazole should not be used by individuals with acute or chronic liver disease. It is also contraindicated for use alongside specific medications, including certain sedatives, heart medications, and cholesterol-lowering drugs, due to the risk of severe adverse events.

Pregnancy

Oral ketoconazole is typically avoided during pregnancy because animal studies have shown it can cause harm to the developing fetus. There is limited information regarding its safety in humans, so it is usually only prescribed if the benefits clearly outweigh the risks.

Topical ketoconazole, including creams and shampoos, is absorbed into the body in very small amounts. While it is generally considered to have a lower risk profile than the oral version, it should still be used with caution and under medical supervision during pregnancy.

Breastfeeding

Oral ketoconazole can pass into breast milk and may cause side effects in a nursing infant. Healthcare providers often recommend either stopping breastfeeding or stopping the medication while treatment is necessary.

For topical ketoconazole, it is unknown if the medication passes into breast milk. If using a topical cream, avoid applying it to the breast area to ensure the infant does not ingest the medication or come into direct skin contact with it.

Topical Formulations

Ketoconazole is most commonly prescribed as a topical medication to treat fungal infections of the skin and scalp. These forms include:

• Cream: Applied directly to the affected skin.
• Shampoo: Used for conditions affecting the scalp, such as dandruff or seborrheic dermatitis.
• Foam: Often used for skin or scalp applications.
• Gel: Applied to the skin for specific fungal conditions.

Oral Formulations

Ketoconazole is also available as an oral tablet. However, the oral form is typically used only when other antifungal treatments are not available or tolerated, due to the risk of serious side effects such as liver damage.

FDA Approval and Indications

Ketoconazole is approved by the U.S. Food and Drug Administration (FDA) to treat various fungal infections. It is available in topical forms, such as creams and shampoos, and as an oral tablet. However, the FDA has significantly narrowed the approved uses for the oral version.

Boxed Warning for Oral Tablets

Oral ketoconazole tablets carry a boxed warning, the FDA’s most serious type of warning, because they can cause severe liver injury (hepatotoxicity) that may lead to liver failure or death. The FDA requires that patients taking the oral form have their liver function monitored closely through blood tests.

Regulatory Restrictions

In 2013, the FDA issued a safety communication limiting the use of oral ketoconazole. Key regulatory points include:

• Limited Use: Oral tablets should only be used for serious fungal infections when no other treatments are available or tolerated by the patient.
• Prohibited Uses: The FDA warns that oral ketoconazole should not be used as a first-line treatment for any fungal infection, nor should it be used for fungal infections of the skin or nails.
• Heart Risks: The medication can interact with other drugs to cause QT prolongation, a serious heart rhythm condition.
• Adrenal Issues: The FDA warns that oral ketoconazole can decrease the body's ability to produce necessary hormones in the adrenal glands.

Topical ketoconazole products, which are applied directly to the skin or scalp, are considered to have a different safety profile and are not subject to the same boxed warnings as the oral tablets.

Common Fungal Infections

Ketoconazole is frequently used in topical forms, such as creams and shampoos, to treat fungal infections on the surface of the body. These conditions include:

• Tinea infections: This group includes ringworm (tinea corporis), athlete's foot (tinea pedis), and jock itch (tinea cruris).
• Tinea versicolor: A fungal infection that causes small, discolored patches of skin.
• Cutaneous candidiasis: Yeast infections that affect the skin.
• Seborrheic dermatitis: A common scalp condition often referred to as dandruff.

Serious Systemic Infections

In its oral tablet form, ketoconazole is used to treat serious, potentially life-threatening fungal infections that spread through the body. Because of the risk of serious side effects, including liver damage, the oral form is typically reserved for infections that cannot be treated with other antifungal medications. These systemic infections may include:

• Blastomycosis
• Histoplasmosis
• Coccidioidomycosis
• Chromomycosis
• Paracoccidioidomycosis

Ketoconazole belongs to a class of drugs known as azole antifungals. It works by interfering with the production of ergosterol, a vital component of fungal cell membranes. This disruption prevents the fungi from growing and spreading, allowing the infection to be cleared.