What Is Enzalutamide (Xtandi<sup>®</sup>)?
Xtandi® (enzalutamide) is an androgen receptor inhibitor, also called an antiandrogen or a nonsteroidal antiandrogen (NSAA). Enzalutamide is a newer kind of NSAA that prevents androgen from binding to the androgen receptor. Enzalutamide is indicated for use in individuals with metastatic (has spread to other parts of the body) and non-metastatic (has not spread to other parts of the body) castrate-resistant prostate cancer (prostate cancer that is not responding to lowering the body’s level of testosterone). Enzalutamide is also approved for metastatic castration-sensitive prostate cancer (prostate cancer that is responsive to lowering the body’s level of testosterone).2,3
Enzalutamide is an orally administered medication that comes in capsule form. Individuals taking enzalutamide should also be monitored for seizures and posterior reversible encephalopathy syndrome (PRES), a reversible condition that affects the brain’s functioning.
How does Xtandi work?
Enzalutamide’s active ingredient is an inhibitor of the androgen receptor in the body. Enzalutamide inhibits the androgen pathway by preventing testosterone and other androgens from binding to androgen receptors. Prostate cancer tumors are often fueled to grow by androgens, including testosterone. Turning off the body’s ability to respond to testosterone can potentially halt tumor growth. Enzalutamide is part of a newer class of NSAA’s, and has a higher affinity for the androgen receptor, meaning it could work more efficiently than previously developed NSAA’s.
Enzalutamide should be taken at the same time as Gonadotropin-Releasing Hormone agonists (GnRH or LHRH) unless you have had surgery to lower the amount of testosterone in your body. In addition, enzalutamide can be used during early stages of other hormone therapies, such as treatment with Gonadotropin-Releasing Hormone agonists, in order to block the initial surge of testosterone that can come along with these medications. The surge of testosterone at the beginning of some of these treatment methods can contribute to a short term rapid tumor growth before it is halted, potentially leading to life-threatening issues such as spinal cord compression.
What are the possible side effects of Xtandi?
Multiple clinical trials evaluated the safety and efficacy of enzalutamide. Possible side effects of enzalutamide include fatigue, hot flashes, loss of appetite, musculoskeletal pain, headache, weight loss, dizziness, high blood pressure, and joint pain. This is not an exhaustive list of all potential side effects of enzalutamide. Talk to your healthcare provider or pharmacist for further information.
Things to note about Xtandi
Several rare but more serious side effects can accompany enzalutamide including seizures and posterior reversible encephalopathy syndrome (PRES). It is important to avoid activities where a sudden loss of consciousness (in the event of a seizure) could cause serious harm to you or others around you. 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 enzalutamide regimen. Alert your provider immediately if you notice any of the following symptoms:
- Loss of consciousness
- Decreased alertness
- Reduced eyesight, blurred vision, or changes in eyesight
- Confusion, falls, or dizziness
- Chest pain or discomfort
- Shortness of breath
Additionally, there is an increased risk of falling or injuries from falls while taking enzalutamide. If you notice signs of a potential infection, or fall and injure yourself, contact your provider immediately.
Before starting enzalutamide talk to your provider if you:
- Have a history of brain injuries, brain tumors, stroke, or seizures
- Have high blood pressure
- Have a partner who is pregnant or could become pregnant
- Have any other medical conditions
- Are currently taking .any other medications (prescription and over-the-counter), vitamins, or herbal supplements
You should also contact your provider if you notice any signs of an allergic reaction to the medication, including chest pain or difficulty breathing. Men who are sexually active with a female partner who could become pregnant should use contraception during treatment and for 3 months after the final dose of enzalutamide (patients should discuss appropriate birth control methods with their doctor). Males having sex with female partners who are pregnant need to use a condom. Enzalutamide may harm an unborn fetus. It is also important to consult the prescribing information for any other medications taken with enzalutamide, including LHRH (or GnRH) agonists.
Enzalutamide is administered orally and may be taken with a LHRH (or GnRH) agonist. Your provider will determine the appropriate dosage and administration schedule for you, as well as the appropriate dosage and administration of any other medications taken with enzalutamide. It is important to follow this schedule exactly as instructed, and not to stop taking enzalutamide or any accompanying medications on your own.1
These are not all the possible side effects of enzalutamide. Patients should talk to their doctor about what to expect with treatment with enzalutamide.