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What Is Enzalutamide (Xtandi®)?

Overview

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. It was previously only indicated for use in individuals with metastatic castrate-resistant prostate cancer (prostate cancer that has spread to other parts of the body and has not previously responded to lowering the body’s level of testosterone). Recently, enzalutamide was approved by the US FDA for use by individuals with non-metastatic castration-resistant prostate cancer (NM-CRPC). Although the castration-resistant indication has not changed, it has been deemed safe and effective for individuals with both metastatic and non-metastatic forms of CRPC to take enzalutamide.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.

What are the ingredients in enzalutamide?

The active ingredient in enzalutamide is enzalutamide, the nonsteroidal antiandrogen.

How does enzalutamide 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 enzalutamide?

Multiple clinical trials evaluated the safety and efficacy of enzalutamide. The most common 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 enzalutamide

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
  • Seizure
  • Headache
  • Decreased alertness
  • Reduced eyesight, blurred vision, or changes in eyesight
  • Confusion, falls, or dizziness
  • Chest pain or discomfort
  • Shortness of breath
  • Fever

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, 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 partner who could become pregnant, should utilize a condom and another form of birth control during treatment and for 3 months after completing treatment. 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.

Dosing information

Enzalutamide is administered orally and may be taken with a LHRH (or GnRH) agonist. Typically, enzalutamide is taken once daily, and comes in a 40 mg capsule. 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. It is important to swallow the enzalutamide capsules whole, and not to crush, chew, or open the capsules.

If you miss a dose of enzalutamide, take your prescribed dose as soon as you remember if it is still within the same day. If you remember the following day, take your regularly scheduled dosage as normal, and do not try to make up for missed doses. It is important not to take more than a single dosage of what you are prescribed each day. Enzalutamide can be taken with or without food. If you take too much enzalutamide, seek emergency medical attention immediately as your risk of seizure may increase.1

Written by: Casey Hribar | Last reviewed: July 2019
  1. Xtandi Prescribing Information. Astellas Pharma. July 2017. Available from: https://www.astellas.us/docs/us/12A005-ENZ-WPI.pdf?v=1
  2. FDA Approved Enzalutamide for Castration-Resistant Prostate Cancer. US Food and Drug Administration. https://www.fda.gov/Drugs/InformationOnDrugs/ApprovedDrugs/ucm613543.htm?utm_campaign=Oncology%207/13/2018%20&utm_medium=email&utm_source=Eloqua&elqTrackId=a5307d59358649b9aee461fb56e8ee55&elq=18bfc6dc0ee143f29ae5abcee90f515a&elqaid=4257&elqat=1&elqCampaignId=3346. Published July 13, 2018. Accessed July 17, 2018.
  3. Phase 3 PROSPER Trial Shows Xtandi (Enzalutamide) Significantly Reduced the Risk of Metastasis or Death by 71 Percent in Men with Non-Metastatic Castration-Resistant Prostate Cancer. Pfizer Inc. https://www.pfizer.com/news/press-release/press-release-detail/phase_3_prosper_trial_shows_xtandi_enzalutamide_significantly_reduced_the_risk_of_metastasis_or_death_by_71_percent_in_men_with_non_metastatic_castration_resistant_prostate_cancer. Published February 5, 2018. Accessed July 17, 2018.