constipation, dizziness or fainting, changes in appetite, thirst, or urine, confusion, memory problems, muscle pain or weakness, fever, rash, itching, or flushing. there may be other side effects. tell your doctor about all your medical conditions, including immune system problems, if you've had or plan to have an organ or stem cell transplant, received chest radiation or have a nervous system problem. depending on the type of cancer, keytruda may be used alone or in combination with other treatments, and is also being studied in hundreds of clinical trials, exploring ways to treat even more types of cancer. it's tru. keytruda from merck. see all the types of cancer keytruda is known for at keytruda.com and ask your doctor if keytruda could be right for you. every day, millions of things need to get to where they're going.