Get emergency medical help if you have signs of an allergic reaction to Keytruda: (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).
Some side effects may occur during the injection. Tell your caregiver if you feel dizzy, light-headed, itchy, hot, sweaty, chilled, or have trouble breathing.
Pembrolizumab affects your immune system, and can cause side effects in many different parts of your body. Some side effects may need to be treated with other medicine.
Call your doctor at once if you have:
sores in your mouth, throat, or nose, or on your genital area;
eye pain or vision problems;
numbness, tingling, burning pain, redness, rash, or blisters on your hands or feet;
severe muscle weakness, severe or ongoing muscle or joint pain;
fever, swollen glands, neck stiffness;
diarrhea or increased stools, severe stomach pain, bloody or tarry stools;
a change in the amount or color of your urine;
liver problems - loss of appetite, right-sided stomach pain, easy bruising or bleeding, dark urine, jaundice (yellowing of the skin or eyes);
low levels of sodium in the body - confusion, slurred speech, severe weakness, loss of coordination, feeling unsteady; or
signs of a hormonal disorder - frequent or unusual headaches, feeling light-headed, rapid heartbeats, hoarse or deepened voice, increased hunger or thirst, increased urination, constipation, hair loss, muscle pain, sweating, feeling cold, weight changes.
Your cancer treatments may be delayed or permanently discontinued if you have certain side effects.
Common Keytruda side effects (some are more likely with combination chemotherapy) may include:
nausea, vomiting, stomach pain, loss of appetite, diarrhea, constipation;
low sodium levels, abnormal liver function or thyroid function tests;
fever, feeling weak or tired;
cough, hoarse voice, feeling short of breath;
itching, rash, or hair loss;
increased blood pressure;
pain in your muscles, bones, or joints; or
soreness in or around your mouth, nose, eyes, throat, or vagina.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Keytruda side effects (more detail)
