Abiraterone (Zytiga) Approved for Metastatic Hormone-Resistant Prostate Cancer

The FDA approved abiraterone (Zytiga) for treatment of castrate-resistant (androgen-independent) metastatic prostate cancer for patients who have received prior chemotherapy containing docetaxel (Taxotere).  The approval was based on an interim analysis of overall survival (OS) in a placebo-controlled randomized trial, each arm receiving prednisone at 5 mg 2x/day orally.  The median OS was 14.8 months in the abiraterone/prednisone group, compared to 10.9 months in the placebo/prednisone group (p<0.0001). 

The most common adverse reactions (>5%) were joint swelling or discomfort, low potassium, edema, muscle discomfort, hot flashes, diarrhea, urinary tract infection, cough, hypertension, arrhythmia, urinary frequency, dyspepsia, nocturia, and upper respiratory tract infection.  Abnormal liver function tests were seen in <1% of patients. 

Abiraterone blood levels were substantially higher when the drug was taken with food (compared to a fasting state).  The recommended dose and schedule for abiraterone is 1000 mg orally once/day, in combination with prednisone 5 mg orally 2x/day.  Abiraterone should be taken on an empty stomach.  No food should be consumed for at least two hours before the dose and for at least one hour after the dose.

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