What Is Abiraterone (Zytiga®)?
Zytiga® (abiraterone) is a CYP17 inhibitor that is used in combination with prednisone. It is indicated for use in individuals with metastatic castration-resistant prostate cancer. It is also approved with prednisone, for metastatic high-risk castration-sensitive prostate cancer (CSPC). Abiraterone is a tablet taken once daily, and the prednisone accompanying it may be prescribed once or twice daily, depending on the exact form of prostate cancer. Patients should also be on a gonadotropin-releasing hormone analog while on abiraterone or should have had bilateral orchiectomy. Individuals taking abiraterone should also be monitored for changes in the number of mineralocorticoids and adrenocorticoids (steroid hormones) in their blood while on the medication, as well as for any signs of changes in liver functioning.
How does abiraterone work?
Abiraterone’s active ingredient is a CYP17 inhibitor. Prostate cancer tumors are often fueled to grow by androgens, including testosterone. Turning off the body’s ability to produce testosterone, or reducing the amount made can potentially halt tumor growth. When the cancer is not responding to treatment with androgen receptor antagonists or other first-line androgen deprivation therapies, the cancer is said to be castrate-resistant. Medications like abiraterone act in different ways, like inhibiting CYP17, to decrease the production of testosterone and other circulating androgens, in attempts to stop the cancer’s growth. CYP17 is an enzyme critical in the pathways involved in producing androgens, like testosterone, as well as other essential molecules in the body, including mineralocorticoids. When the pathway to making testosterone and other androgens is blocked, tumor growth may be suppressed.
What are the possible side effects of abiraterone?
Multiple clinical trials evaluated the safety and efficacy of abiraterone. The most common side effects of abiraterone include joint swelling or discomfort, muscle discomfort, fluid retention (edema), hot flashes, diarrhea, high blood pressure, cough, upper respiratory tract infection, gastrointestinal distress, fatigue, low potassium, and headache. This is not an exhaustive list of all potential side effects of abiraterone. Talk to your healthcare provider or pharmacist for further information.
Things to note about abiraterone
Several rare but more serious side effects can accompany abiraterone including problems with your adrenal glands (glands that assist in hormone production) and liver problems. Individuals should be closely monitored for signs of these serious side effects. Additionally, abiraterone could cause other serious side effects including low blood potassium levels, high blood sugar, sodium, and cholesterol levels, fluid retention (edema), and high blood pressure. Patients should take their medication as prescribed by their doctor. Patients should talk to their doctor if they have any questions, or if they have questions regarding their abiraterone regimen. Alert your provider immediately if you notice any of the following symptoms:
- Fast heartbeat
- Feeling lightheaded or faint
- Pain or swelling in your legs or feet
- Muscle weakness
- Yellowing of the skin or whites of eyes (jaundice)
- Brown urine
- Severe nausea or vomiting
You should also contact your provider if you notice any signs of an allergic reaction to the medication, including chest pain or difficulty breathing. It is also important to consult the prescribing information for any other medications taken with abiraterone, including prednisone.
Before starting abiraterone talk to your provider if you:
- Have any heart problems
- Have adrenal, pituitary, or liver problems
- Have any other medical conditions
- Are currently taking any other medications (prescription and over-the-counter), vitamins, or herbal supplements
Abiraterone is administered orally and in combination with prednisone. Your provider will determine the appropriate dosage and administration schedule for you. It is important to follow this schedule exactly as instructed, and not to stop taking abiraterone or prednisone on your own. Men who are sexually active with pregnant women or women who may become pregnant should use appropriate contraceptive methods during treatment with abiraterone and for three weeks after stopping abiraterone (patients should discuss appropriate birth control methods with their doctor).1
These are not all the possible side effects of abiraterone. Patients should talk to their doctor about what to expect with treatment with abiraterone.