Abiraterone Acetate: CYP17 Inhibitor for Advanced Prostate Cancer

Abiraterone Acetate is an oral medication classified as a CYP17 inhibitor. It is used in combination with a corticosteroid (such as Prednisone) to treat metastatic castration-resistant prostate cancer (mCRPC) and metastatic high-risk castration-sensitive prostate cancer (CSPC).

1. Mechanism of Action

Androgens (male hormones) promote prostate tumor growth. Abiraterone works by irreversibly inhibiting the CYP17 enzyme (17α-hydroxylase/C17,20-lyase). This action blocks the synthesis of androgens not only in the testes but also in the adrenal glands and within the tumor tissue itself, thereby starving the cancer of its fuel source.

2. Dosage and Administration

• Standard Dose:​ 1000 mg (two 500 mg tablets) taken orally once daily on an empty stomach.

• Micro-Particulate Formulations:​ Some brands may use a 500 mg daily dose. Always follow the specific prescription.

• Mandatory Corticosteroid:​ Must be taken concurrently with Prednisone (typically 5 mg twice daily) or another corticosteroid to prevent mineralocorticoid excess and adrenal crisis.

• Food Restriction:​ Take on an empty stomach. Do not eat for at least 2 hours before and 1 hour after taking the medication. Food drastically increases absorption and toxicity.

• Administration:​ Swallow tablets whole with water. Do not crush, chew, or break them.

3. Critical Warnings and Contraindications

• Hepatotoxicity:​ Severe liver injury can occur. Baseline liver function tests (LFTs) are required before starting and must be monitored regularly. Contraindicated in patients with severe liver impairment (Child-Pugh Class C).

• Fetal Toxicity:​ Abiraterone can cause fetal harm. It is contraindicated in women who are or may become pregnant. Male patients with pregnant partners must use a condom during treatment and for 1 week after the last dose. If the partner is of childbearing potential, use a condom plus another effective contraceptive method.

• Drug Interactions:​ Avoid St. John’s Wort. Use caution with diabetes medications like pioglitazone or repaglinide.

4. Monitoring and Side Effects

• Cardiovascular:​ Monitor blood pressure, heart rate, and for signs of fluid retention or heart failure.

• Electrolytes:​ Monitor for hypokalemia (low potassium) and hyperglycemia (high blood sugar).

• Common Side Effects:​ Fatigue, joint pain, hypertension, edema, hot flashes, and diarrhea.

• Serious Side Effects:​ Seek immediate medical attention for severe allergic reactions, chest pain, irregular heartbeat, severe leg pain/swelling, or signs of liver damage (jaundice, dark urine, right upper abdominal pain).