Keytruda may potentially cause side effects ranging from mild to severe. The list below includes some of the most common side effects but is not a complete list. Mild side effects may go away after a few days or weeks of consistent medication-taking, but if they persist or worsen you should speak with your doctor. Common side effects: Stomach pain Cough Constipation Loss of appetite Muscle aches Nausea Fatigue Shortness of breath Fever Serious side effects: Colitis (fever, diarrhea, bloating) Hepatitis (itchy skin, yellowing skin, nausea) Hypothyroidism (depression, dry skin, constipation, fatigue) Nephritis (frequent urination, burning sensation when urinating, pelvic pain)
If you experience any of these serious side effects, you should speak with your doctor or seek immediate medical attention if it is an emergency. In some rare cases, patients can experience allergic reactions. Seek emergency medical care if you experience any of the following symptoms after taking Keytruda. Skin rash Wheezing Tightness in the throat or chest Difficulty talking or breathing Swelling of the face, lips, tongue, or throat