Xtandi is a prescription drug used to treat prostate cancer in adults. Learn about side effects of the drug and how to manage them. Xtandi is approved to treat prostate cancer in males.* It , Serious side effects of Xtandi. Along with its needed effects, enzalutamide (the active ingredient contained in Xtandi) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention. Check with your doctor immediately if any of the following side effects occur while taking , Enzalutamide is a medication used to treat prostate cancer in adult males. Common side effects of enzalutamide include fatigue, weakness, decrease in hemoglobin level, decrease in count of neutrophil immune cells, decrease in white blood cell count, high blood glucose level (hyperglycemia), electrolyte disturbances, back pain, joint pain (arthralgia), musculoskeletal pain, muscular weakness , , , .