Keytruda can cause the immune system to attack normal organs and tissues in any area of the body and can affect the way they work. These problems can sometimes become serious or life-threatening and can lead to death.
Common side effects of Keytruda include: feeling tired, pain in muscles, bones or joints, decreased appetite, itching, diarrhea, nausea, rash, fever, cough, shortness of breath, and constipation.
In children, feeling tired, vomiting and stomach-area (abdominal) pain, and increased levels of liver enzymes and decreased levels of salt (sodium) in the blood are more common than in adults.
Call or see your doctor right away if you develop any symptoms of the following problems or these symptoms get worse:
- Lung problems (pneumonitis). Symptoms of pneumonitis may include: shortness of breath, chest pain, new or worse cough.
- Intestinal problems (colitis) that can lead to tears or holes in the intestine. Signs and symptoms of colitis may include: diarrhea or more bowel movements than usual, stools that are black, tarry, sticky, or have blood or mucus, severe stomach-area (abdomen) pain or tenderness.
- Liver problems (hepatitis). Signs and symptoms of hepatitis may include: yellowing of the skin or the whites of the eyes, nausea or vomiting, pain on the right side of the stomach area (abdomen), dark urine, feeling less hungry than usual, bleeding or bruising more easily than normal.
- Hormone gland problems (especially the thyroid, pituitary, adrenal glands, and pancreas). Signs and symptoms that the hormone glands are not working properly may include: rapid heart beat, weight loss or weight gain, increased sweating, feeling more hungry or thirsty, urinating more often than usual, hair loss, feeling cold, constipation, the voice gets deeper, muscle aches, dizziness or fainting, headaches that will not go away or unusual headache.
- Kidney problems, including nephritis and kidney failure. Signs of kidney problems may include: change in the amount or color of the urine.
- Skin problems. Signs of skin problems may include: rash, itching, blisters, peeling or skin sores, painful sores or ulcers in the mouth or in the nose, throat, or genital area.
- Problems in other organs. Signs of these problems may include: changes in eyesight severe or persistent muscle or joint pains, severe muscle weakness, low red blood cells (anemia), shortness of breath, irregular heartbeat, feeling tired, or chest pain (myocarditis).
- Infusion (IV) reactions, that can sometimes be severe and life-threatening. Signs and symptoms of infusion reactions may include: chills or shaking, shortness of breath or wheezing, itching or rash, flushing, dizziness, fever, feeling like passing out.
- Rejection of a transplanted organ. People who have had an organ transplant may have an increased risk of organ transplant rejection if they are treated with Keytruda.
- Complications of stem cell transplantation that uses donor stem cells (allogeneic) after treatment with Keytruda. These complications can be severe and can lead to death.
Getting medical treatment right away may help keep these problems from becoming more serious.
Tell your doctor if you have any side effect that bothers you or that does not go away.