How does this medication work? What will it do for me?

Enzalutamide belongs to the class of medications called antineoplastic endocrine therapies. Specifically, enzalutamide is an androgen receptor inhibitor. This medication is used to treat metastatic prostate cancer (cancer that has spread to other parts of the body) in people who have received medications or had surgery to lower testosterone levels, or have received prior cancer treatment with docetaxel.

Androgens are male hormones and include testosterone. Prostate cancer cells require testosterone in order to grow and reproduce. Enzalutamide blocks the action of male hormones such as testosterone that tell the cancer cells to grow. This slows the growth of prostate cancer.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Each white to off-white, oblong, liuid filled, soft capsule with the letters "ENZ" printed in black contains 40 mg of enzalutamide. Nonmedicinal ingredients: caprylocaproyl macrogolglycerides, butylhydroxyanisole (E320), butylhydroxytoluene (E321). Capsule shell: gelatin, sorbitol sorbitan solution, glycerol, titanium dioxide (E171), and purified water. Printing ink: ethanol, ethyl acetate, propylene glycol, iron oxide black (E172), polyvinyl acetate phthalate, purified water, isopropyl, alcohol, macrogol 400, and ammonia solution concentrated.

How should I use this medication?

The recommended adult dose of enzalutamide is 160 mg (four 40 mg capsules) taken once daily as a single dose. This medication may be taken with food or on an empty stomach. Swallow the capsules whole, with water.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take enzalutamide if you:

  • are allergic to enzalutamide or any ingredients of the medication
  • are breast-feeding
  • are or may be pregnant

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • anxiety
  • drowsiness
  • dry, itchy skin
  • falls
  • fatigue
  • forgetfulness
  • headache
  • hot flush

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • abnormal heart rhythms (such as fast or slow heart rate, palpitations), fainting or seizures
  • bone fractures
  • breast enlargement
  • bruising
  • difficulty remembering
  • difficulty solving problems
  • hallucinations (e.g., seeing or hearing things that aren't there)
  • increased blood pressure
  • nosebleeds
  • problems concentrating
  • restless legs
  • signs of infection (symptoms may include fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness)

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • seizures

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Abnormal heart rhythms: This medication can cause abnormal heart rhythms. Certain medications (e.g., sotalol, quinidine, thioridazine, chlorpromazine, droperidol, pimozide, gatifloxacin, moxifloxacin, mefloquine, pentamidine, arsenic trioxide, dolasetron mesylate, probucol, tacrolimus) can increase the risk of a type of abnormal heart rhythm called QT prolongation, and should not be used in combination with enzalutamide. You are more at risk for this type of abnormal heart rhythm and its complications if you:

  • are female
  • are older than 65 years of age
  • have a family history of sudden cardiac death
  • have a history of heart disease or abnormal heart rhythms
  • have a slow heart rate
  • have congenital prolongation of the QT interval
  • have diabetes
  • have low potassium, magnesium, or calcium levels
  • have nutritional deficiencies
  • have had a stroke

If you have heart disease and abnormal heart rhythms, or if you are taking certain medications (e.g., verapamil, atazanavir), discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Blood disorders: This medication can cause the levels of certain blood cells to drop. This may lead to problems with blood clotting, or the immune system. Contact your doctor immediately if you develop a fever, chills, easy bruising, or bleeding (symptoms may include black and tarry stools, blood in the urine, or cuts that won't stop bleeding) while taking this medication. Your doctor will arrange periodic blood testing to monitor various blood components.

Blood pressure: Enzalutamide may cause high blood pressure. Your doctor should monitor your blood pressure regularly while you are taking this medication.

Posterior Reversible Encephalopathy Syndrome: Very rarely, this medication can cause a reversible brain problem called PRES (posterior reversible encephalopathy syndrome). If you develop a seizure, headache, weakness, confusion, loss of vision, or other vision changes while using this medication, get immediate medical attention.

Reduced alertness: Enzalutamide may affect the mental abilities needed to drive or operate machinery, such as concentration, problem solving and focused attention. Avoid driving, operating machinery, or performing other hazardous tasks until you have determined how this medication affects you.

Seizures: There have been reports of seizures occurring with enzalutamide. Seizures are more likely to occur when higher doses of this medication are taken or in people who have been previously treated with docetaxel. If you have a history of epilepsy or medical conditions that increase the risk of seizures, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Pregnancy: Enzalutamide should not be used by women. It is not known if enzalutamide is found in semen. If you are engaged in sexual activity with a pregnant woman, a condom should be used. If you are engaged in sexual activity with a woman who may become pregnant, you should use a condom and a second effective method of birth control. Condoms must be used during treatment with enzalutamide and for 3 months after treatment has ended to avoid possible contact between a developing fetus and the medication. To prevent accidental exposure to enzalutamide, women who handle these tablets should wear gloves.

Breast-feeding: Enzalutamide should not be used by women. It is not known if enzalutamide passes into breast milk. To prevent accidental exposure to enzalutamide, women who handle these tablets should wear gloves.

Children: The safety and effectiveness of using this medication have not been established for children.

What other drugs could interact with this medication?

There may be an interaction between enzalutamide and any of the following:

  • abiraterone acetate
  • alpha blockers (e.g., alfuzosin, doxazosin, tamsulosin)
  • amiodarone
  • anti-psychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
  • apixaban
  • aprepitant
  • avanafil
  • "azole" antifungals (e.g., itraconazole, ketoconazole, voriconazole)
  • benzodiazepines (e.g., clonazepam, diazepam, lorazepam)
  • bisoprolol
  • boceprevir
  • bosentan
  • buprenorphine
  • buspirone
  • busulfan
  • calcitriol
  • calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil)
  • cancer medications (e.g., docetaxel,  doxorubicin, etoposide, ifosfamide, vinblastine, vincristine)
  • carbamazepine
  • celecoxib
  • chloroquine
  • cobicistat
  • conivaptan
  • corticosteroids (e.g., dexamethasone, hydrocortisone, methylprednisolone, prednisone)
  • cyclosporine
  • dabrafenib
  • dantrolene
  • dapsone
  • dasatinib
  • deferasirox
  • dexamethasone
  • disopyramide
  • dronedarone
  • eplerenone
  • ergot alkaloids (e.g., ergotamine, dihydroergotamine)
  • estrogens (e.g., estradiol, ethinyl estradiol)
  • ethosuximide
  • everolimus
  • exemestane
  • flutamide
  • fosaprepitant
  • gemfibrozil
  • guanfacine
  • HIV non-nucleoside reverse transcriptase inhibitors (e.g., delaviridine, efavirenz, etravirine, nevirapine)
  • HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir)
  • isosorbide dinitrate or mononitrate
  • lidocaine
  • macrolide antibiotics (e.g., clarithromycin, erythromycin)
  • maraviroc
  • mefloquine
  • methadone
  • mifepristone
  • mirtazapine
  • modafinil
  • montelukast
  • narcotic pain relievers (e.g., codeine, fentanyl, morphine, oxycodone)
  • nateglinide
  • nefazodone
  • ondansetron
  • paclitaxel
  • phenobarbital
  • phenytoin
  • pimozide
  • praziquantel
  • primaquine
  • progestins (e.g., norethindrone, norgesterel, medroxyprogesterone)
  • proton pump inhibitors (e.g., lansoprazole, omeprazole)
  • quinidine
  • quinine
  • regorafenib
  • repaglinide
  • rifabutin
  • rifampin
  • rilpivirine
  • rivaroxaban
  • roflumilast
  • romidepsin
  • selective serotonin reuptake inhibitors (SSRIs; e.g., citalopram, duloxetine, fluoxetine, paroxetine, sertraline)
  • sildenafil
  • silodosin
  • sirolimus
  • solifenacin
  • "statin" anti-cholesterol medications (e.g., atorvastatin, lovastatin, simvastatin)
  • St. John's wort
  • tacrolimus
  • tadalafil
  • tamoxifen
  • telaprevir
  • temsirolimus
  • tetracycline
  • theophylline
  • thiazolidinediones (e.g., pioglitazone, rosiglitazone)
  • ticlopidine
  • ticagrelor
  • tolterodine
  • tolvaptan
  • tramadol
  • trazodone
  • trimethoprim
  • trimipramine
  • tyrosine kinase inhibitors (e.g., vandetanib, sunitinib, nilotinib)
  • venlafaxine
  • vorinostat
  • warfarin
  • zolpidem
  • zopiclone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.