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Ketoconazole

Ketoconazole: Generic Medication Overview

This article covers Ketoconazole, available as a generic medication and marketed under brand names such as Nizoral. It is an antifungal agent classified within the Antifungals therapeutic group and is supplied as a 200 mg oral pill. In Hong Kong, ketoconazole is a prescription-only product regulated by the Department of Health.

How Ketoconazole Works in the Body

Ketoconazole belongs to the azole class of antifungals. It inhibits the fungal enzyme lanosterol 14α-demethylase, a key step in the synthesis of ergosterol, an essential component of fungal cell membranes. By blocking ergosterol production, the drug destabilizes the membrane, leading to increased permeability and eventual cell death. Oral ketoconazole is absorbed from the gastrointestinal tract, reaches peak plasma concentrations within 1-2 hours, and has a half-life of approximately 8 hours. The medication is extensively metabolized in the liver and excreted mainly in the feces.

Conditions Treated with Ketoconazole

Ketoconazole is approved in many jurisdictions for systemic fungal infections caused by susceptible yeasts and molds, including:

• Blastomycosis
• Histoplasmosis (particularly chronic pulmonary forms)
• Coccidioidomycosis (when alternative agents are unavailable)

In Hong Kong, the Department of Health permits oral ketoconazole for these indications when the benefits outweigh the risk of liver toxicity. The drug is not indicated for superficial skin infections, which are treated with topical formulations.

Patient Suitability and Contraindications

Who Should Use Ketoconazole?

• Adults with confirmed systemic fungal infection susceptible to azole therapy.
• Patients with normal hepatic function and no history of severe liver disease.

Absolute Contraindications

• Known hypersensitivity to ketoconazole or any azole antifungal.
• Pre-existing severe hepatic impairment (e.g., Child-Pugh class C).
• Concurrent use of drugs that are strong CYP3A4 substrates and cannot be safely discontinued (e.g., certain anti-arrhythmics, immunosuppressants).

Relative Contraindications

• Mild to moderate liver disease; requires close monitoring of liver enzymes.
• Pregnancy (Category C) - ketoconazole may cause fetal harm; it is contraindicated in the first trimester.
• Lactation - excreted in breast milk; breastfeeding is not recommended while on therapy.

Special Populations

• Elderly: May have reduced hepatic clearance; dose adjustment is often unnecessary but monitoring is prudent.
• Renal Impairment: No dose change required unless accompanied by hepatic dysfunction.

Safety Profile: Side Effects and Interactions

Common Side Effects

• Nausea, abdominal discomfort, or vomiting (commonly reported).
• Headache or dizziness.
• Mild elevations in liver enzymes (ALT/AST) that are usually transient.

Serious Adverse Events

• Hepatotoxicity: Severe liver injury, hepatitis, or hepatic failure can occur; patients should seek immediate medical attention for jaundice, dark urine, or right-upper-quadrant pain.
• Adrenal Suppression: Ketoconazole can inhibit steroid synthesis, leading to fatigue, hypotension, or electrolyte abnormalities.
• QT Prolongation: Rare cases of cardiac arrhythmia have been reported, especially when combined with other QT-prolonging agents.

Drug Interactions

• Major Interactions - Ketoconazole is a potent inhibitor of the CYP3A4 enzyme. It can increase plasma concentrations of drugs such as:

• Cyclosporine, sirolimus, and tacrolimus (immunosuppressants).

• Midazolam, triazolam, and other benzodiazepines.

• Statins metabolized by CYP3A4 (e.g., simvastatin, lovastatin), raising the risk of myopathy.

• Moderate Interactions - May require dose adjustment or increased monitoring:

• Warfarin (possible increased INR).

• Oral contraceptives (reduced effectiveness).

Patients should disclose all medications, including over-the-counter products and herbal supplements, before starting ketoconazole.

Food and Lifestyle Interactions

• Food: Taking the pill with a low-fat meal enhances absorption; a high-fat meal can increase bioavailability and may raise the risk of liver irritation.
• Alcohol: Concomitant alcohol use can worsen hepatic side effects; moderation or avoidance is advised.
• Driving: Dizziness may occur; patients should assess their ability to operate machinery safely.

How to Take Ketoconazole

• Standard Dosing: One 200 mg tablet taken orally once daily, preferably with a low-fat meal.
• Special Populations:
• Mild hepatic impairment: Continue with the standard dose but monitor liver function tests (LFTs) every 2-4 weeks.
• Severe hepatic impairment: Ketoconazole is contraindicated.
• Administration Tips: Swallow the tablet whole with a glass of water; do not crush or chew.
• Missed Dose: Take the missed dose as soon as remembered unless it is close to the time of the next scheduled dose. Do not double the dose.
• Overdose: Symptoms may include nausea, vomiting, abdominal pain, and severe liver dysfunction. Seek emergency medical care; activated charcoal may be considered if presentation is early.
• Discontinuation: No taper is required for short-term courses; however, abrupt cessation after long-term therapy may reveal adrenal suppression, so a gradual reduction under medical supervision is advisable.

Monitoring and Follow-Up

• Baseline Tests: Liver function tests (ALT, AST, bilirubin) before initiating therapy.
• Routine Monitoring: Repeat LFTs every 2 weeks for the first 2 months, then monthly thereafter.
• Clinical Assessment: Monitor for signs of adrenal insufficiency (fatigue, hypotension) and cardiac symptoms if taking QT-prolonging drugs.
• When to Contact a Provider: Any new jaundice, dark urine, severe abdominal pain, unexplained bruising, or palpitations.

Storage and Handling

• Store tablets at room temperature (15-30 °C), away from direct sunlight and moisture.
• Keep the container tightly closed and out of reach of children.
• Do not use the medication past the expiration date printed on the packaging.
• Dispose of unused tablets according to local pharmaceutical waste guidelines or return them to a pharmacy.

Medication-Specific Glossary

CYP3A4

A liver enzyme that metabolizes many drugs; ketoconazole inhibits this enzyme, raising levels of co-administered medications.

Hepatotoxicity

Chemical injury to the liver that can manifest as enzyme elevation, hepatitis, or liver failure.

QT Prolongation

Extension of the heart’s electrical repolarization period, increasing the risk of abnormal rhythms.

Adrenal Suppression

Reduced production of cortisol and other adrenal hormones due to inhibition of steroid synthesis.

Ergosterol

A sterol component of fungal cell membranes; its synthesis is blocked by ketoconazole.

Azole Antifungal

A class of drugs that target fungal lanosterol 14α-demethylase, disrupting cell membrane formation.

Medical Disclaimer

This article provides educational information about Ketoconazole and is not a substitute for professional medical advice. Treatment decisions, including use for unapproved indications, must be made under the guidance of a qualified healthcare provider. The content is intended for informational purposes and does not constitute medical recommendations. Always consult a physician before starting, stopping, or changing any medication regimen.