Capecitabine is a highly effective and well-tolerated therapy for breast cancer gastric cancer and colorectal cancer. Take this medication by mouth as directed by your doctor, usually 2 times a day. Do not crush or split the tablets. It is not advised for pregnant women as it may cause harm to an unborn baby. Nausea, vomiting, loss of appetite, constipation, tiredness are some common side effects of capecitabine 500 mg.