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Xtandi: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on Dec 8, 2020.

1. How it works

  • Xtandi is a brand (trade) name for enzalutamide which is an antiandrogen that may be used to treat certain types of prostate cancer.
  • Enzalutamide blocks male sex hormones (androgens) from binding to androgen receptors. Early prostate cancers need relatively high levels of androgens to grow. Since the testes are the main source of androgens, androgen deprivation therapy (ADT) is a common treatment for androgen-sensitive prostate cancer. After a time, however, most prostate cancers become castrate-resistant, which means they can grow even when androgen levels in the blood are very low. Because ADT does not block the production of the small amounts of androgen made by the adrenal glands and prostate cancer cells themselves, this low level is sufficient to fuel the growth of castrate-resistant prostate cancers. Enzalutamide keeps this small amount of androgen from binding to androgen receptors, starving the prostate cancer cells of androgens needed to grow.
  • Xtandi belongs to the class of medications known as androgen receptor inhibitors.

2. Upsides

  • May be used to treat men with castration-resistant prostate cancer or metastatic castration-sensitive prostate cancer.
  • Used in combination with a gonadotropin-releasing hormone (GnRH) analog unless the man has had a bilateral orchidectomy.
  • Available as a capsule or a tablet which are taken by mouth (orally) once a day.
  • Two tablet strengths are available, 40mg and 80mg. Once capsule strength is available: 40mg. The recommended dose is 160mg once daily.
  • Xtandi is not a chemotherapy medication.
  • Most men prescribed Xtandi were over the age of 65. No differences in safety or effectiveness were noted.
  • No dosage adjustment is needed in mild-to-moderate kidney disease. Safety in severe kidney disease is not known. No initial dosage adjustment is needed in mild, moderate, or severe hepatic impairment.
  • Does not appear to affect the QT interval.
  • Extends survival in men with metastatic prostate cancer that had progressed during treatment with androgen deprivation therapy.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Weakness or lack of energy; back, muscle, or joint pain; diarrhea, hot flushes, edema, urinary problems, edema, insomnia, infections, dizziness, abnormal sensation of the skin (tingling, pricking, chilling, burning, numbness) with no apparent physical cause, gynecomastia (enlarged breasts in men), vomiting, and anxiety are some of the most common side effects reported. Men may also experience a decrease in appetite and weight decrease.
  • Changes in laboratory tests such as low neutrophils or white blood cells, high blood sugars, high magnesium or calcium levels, or low sodium levels have been reported.
  • Men receiving Xtandi are at increased risk of high blood pressure. Monitor for signs and symptoms of cardiovascular disease.
  • Has been associated with an increased risk of falls and fractures. Warn patients to be careful when moving around.
  • Rarely may cause hypersensitivity reactions including edema of the face, tongue, lip, or throat.
  • May increase the risk of seizures. Risk is higher in those with a previous history of seizures or epilepsy, taking other medications that also lower the seizure threshold such as bupropion or SSRIs, a previous head injury, cerebrovascular disease, Alzheimer's disease, CNS anomalies, unexplained loss of consciousness in the past 12 months, or a history of arteriovenous malformation or brain infection.
  • Posterior Reversible Encephalopathy Syndrome (PRES) has been reported in men taking Xtandi. PRES is a neurological disorder that can develop rapidly and cause symptoms such as headache, seizures, confusion, lethargy, blindness, and other visual and neurological disturbances, with or without high blood pressure. If PRES is suspected perform brain imaging, preferably an MRI. Discontinue Xtandi if PRES develops.
  • Xtandi is only approved for use in men. Men who have female partners of reproductive potential should use effective contraception during treatment with Xtandi and for 3 months after the last dose. May impair fertility in males of reproductive potential.
  • Xtandi is not available as a generic.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

4. Bottom Line

Xtandi is an androgen receptor inhibitor that is usually used in conjunction with androgen deprivation therapy for the treatment of prostate cancer. The main side effects are weakness or lack of energy, pain, and hot flushes. Xtandi has been shown to increase survival.

5. Tips

  • Take Xtandi exactly as prescribed by your doctor. The usual dose is 160mg once daily. Swallow the tablets or capsules whole, do not crush or cut the tablets or open the capsules. Xtandi is always usually administered with a GnRH analog, such as Lupron Depot or Zoladex, unless you have already had a bilateral orchidectomy.
  • Xtandi may be taken with or without food. Try to take Xtandi at the same time every day.
  • If you have diabetes, you may need to monitor your blood sugar levels more regularly while being treated with Xtandi.
  • Xtandi may increase your risk of falls or fracturing a bone. Ensure there are no tripping hazards around your home and be careful when getting out of bed or going up or downstairs.
  • Xtandi may increase your risk for cardiovascular disease. Ensure you eat a healthy diet, exercise, don't smoke, and take your medications as directed by your doctor for any coexisting conditions, such as high cholesterol or diabetes. If you experience any chest pain or pain that radiates down your arm or up your neck, seek urgent medical attention.
  • See your doctor immediately if you develop any side effects of concern including shortness of breath or difficulty breathing, edema or swelling of the face or throat, sudden headache, vomiting, visual changes, or confusion. Xtandi has been associated with an increased risk of seizures.
  • Xtandi may affect your fertility. Talk to your doctor if you are planning to have a family in the future. If you have a female partner of reproductive potential use effective contraception during treatment with Xtandi and for 3 months after the last dose. Xtandi can cause fetal harm and miscarriage.
  • Tell your doctor or pharmacist that you are taking Xtandi and do not take any other medications, including those brought over the counter from a supermarket or pharmacy, without talking to your doctor first.

6. Response and Effectiveness

  • The AFFIRM trial investigated Xtandi versus placebo in metastatic CRPC following chemotherapy. A significant improvement in overall survival was noted in men treated with Xtandi compared with those treated with placebo (an inactive treatment). 53.1% of patients treated with placebo died compared to 38.5% of those treated with Xtandi. The median survival was 13.6 months with placebo compared with 18.4 months with Xtandi.
  • The PREVAIL trial investigated Xtandi versus placebo in chemotherapy-naive metastatic CRPC. The overall number of deaths was 35% in men treated with placebo compared with 28% in those treated with Xtandi. An updated survival analysis was conducted when 784 deaths were observed. The median follow up time was 31 months. By that time 49% of placebo-treated patients had died compared with 42% of those receiving Xtandi.

7. Interactions

Medicines that interact with Xtandi may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with Xtandi. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

There are over 550 medications that have major or moderate interactions with Xtandi. Some common medications that may interact with Xtandi include:

  • acid control treatments such as antacids, famotidine, or omeprazole
  • albuterol
  • alfentanil or fentayl
  • antibiotics, such as erythromycin, levofloxacin, or metronidazole
  • anticancer treatments such as doxorubicin
  • antidepressants, such as amitriptyline, citalopram, escitalopram, or venlafaxine
  • antidiarrheal medications, such as loperamide
  • antiepileptics, such as carbamazepine
  • antifungals, such as azithromycin or fluconazole
  • antihistamines, such as hydroxyzine
  • antipsychotics, such as aripiprazole, clozapine, haloperidol, thioridazine, or ziprasidone
  • apixaban
  • bisacodyl
  • bupropion
  • chloroquine or hydroxychloroquine
  • cisapride
  • codeine
  • cyclosporine
  • digoxin
  • ergotamine or dihydroergotamine
  • heart medications, such as amiodarone, felodipine, or flecainide
  • HIV medications, such as efavirenz or saquinavir
  • insulin and other antidiabetic medications such as glibenclamide, glyburide, or metformin
  • lactulose
  • levonorgestrel and other hormones
  • lithium
  • magnesium salts
  • methadone, oxycodone, and other opiates
  • midazolam
  • mineral oil
  • montelukast
  • moxifloxacin
  • multiple sclerosis agents such as fingolimod or ozanimod
  • ondansetron
  • oxytocin
  • papaverine
  • pimozide
  • quinidine
  • salmeterol
  • senna
  • sirolimus and tacrolimus
  • St John's Wort
  • tamoxifen
  • tolbutamide
  • tramadol
  • warfarin (conduct additional monitoring).

Xtandi should not be given at the same time as strong CYP2C8 inhibitors, such as gemfibrozil, clopidogrel, felodipine, mometasone, zafirlukast, erlotinib, dabrafenib, candesartan, or salmeterol, if possible. If coadministration is unavoidable, reduce the dose of Xtandi to 80mg once daily. Return the Xtandi dose back to 160mg/day or the dose previously prescribed when the strong CYP2C8 inhibitor is discontinued.

Xtandi should not be given at the same time as strong CYP2C8 inducers, such as rifampicin, secobarbital, phenobarbital, or phenytoin. If coadministration is unavoidable, increase the dose of Xtandi to 240mg once daily. Return the Xtandi dose back to 160mg/day or the dose previously prescribed when the strong CYP2C8 inhibitor is discontinued.

Xtandi is also a moderate CYP2C9 and CYP2C19 inducer.

Note that this list is not all-inclusive and includes only some common medications that may interact with Xtandi. You should refer to the prescribing information for Xtandi for a complete list of interactions.

References

Xtandi (enzalutamide) [Package Insert]. Updated 08/2020. Manufactured by Pfizer Pharmaceuticals LLC, for Astellas Pharma US, Inc., Northbrook, IL 60062. https://www.drugs.com/pro/xtandi.html

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Xtandi only for the indication prescribed.

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