What should I know about Xtandi before taking it?

Before you take Xtandi (enzalutamide), you should know that it is approved for men with castration-resistant prostate cancer that has spread to other parts of the body; that means their cancer is resistant to medical or surgical treatments that lower testosterone. People who take Xtandi should have already tried another medication, docetaxel.

Your doctor will most likely prescribe four 40 milligram (mg) capsules of Xtandi once per day. You should not change your dose or stop taking Xtandi without first consulting your physician. Swallow the capsules whole. Do not dissolve, chew or open the capsules. You can take Xtandi with or without food.

Xtandi is for men only. This drug can be harmful to a developing fetus so, if you are taking Xtandi, do not have sex with a pregnant woman without using a condom; you should do this for three months after you stop taking Xtandi. If you have sex with a woman who could become pregnant, use a condom and another form of birth control; you should do this for three months after you stop taking Xtandi.

Xtandi can interact with a number of drugs, in some cases increasing the risk of side effects and in others possibly making Xtandi less effective. Some supplements may interact with Xtandi, too. Xtandi can also affect how well certain other drugs work. Before you start taking Xtandi, tell your doctor about all your other medications (prescription and over-the-counter), as well as any supplements you take. Once you're on Xtandi, talk with your doctor before taking a new drug or supplement. If you take warfarin, you should have additional testing to see how long it takes for your blood to clot.

You should know that Xtandi may cause seizures. You should not participate in activities where a sudden loss of consciousness could result in serious harm to yourself or others. Xtandi may also cause:

• dizziness
• clouded thinking
• numbness and tingling
• decreased sensation in the skin
• falls

Before you start taking Xtandi, give your doctor a complete medical history. Tell him or her about all your other medications, whether they're prescription or over-the-counter, as well as dietary and herbal supplements. Once you're on Xtandi, do not start taking another drug or supplement without talking with your doctor first.