see your doctor right away if you have cough, shortness of breath, chest pain, diarrhea, severe stomach pain, severe nausea or vomiting, headache, light sensitivity, eye problems, irregular heartbeat, extreme tiredness, 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. it feels good to be here for them. living longer is possible. it's tru. keytruda from merck. ask your doctor about keytruda.