​Pembrolizumab (Generic Name)

Other Names: Keytruda®

About This Drug  

Penbrolizumab is used to treat cancer. It is given in the vein (IV). 

Possible Side Effects (More Common)

  • Loose bowel movements (diarrhea) that may last for a few days
  • Constipation (not able to move bowels)
  • Nausea and throwing up (vomiting). These symptoms may happen within a few hours after your treatment and may last up to 24 hours. Medicines are available to stop or lessen these side effects.
  • Generalized weakness and discomfort (aches or pains)
  • Rash
  • Feeling tired
  • Decreased appetite (decreased hunger)

Possible Side Effects (Less Common)

  • Colitis which is swelling in the colon.  The symptoms are loose bowel movements (diarrhea) stomach cramping, and sometimes blood in the bowel movements.
  • Changes in your liver function.  Your doctor will check your liver function as needed.
  • This drug may affect how your kidneys work. Your kidney function will be checked as needed. 
  • Changes in lung tissue may happen with large amounts of this drug. These changes may not last forever, and your lung tissue may go back to normal. You may get a cough or have trouble catching your breath.

Treating Side Effects

  • Ask your doctor or nurse about medicines that are available to help stop or lessen constipation.
  • If you are not able to move your bowels, check with your doctor or nurse before you use any enemas, laxatives, or suppositories
  • Ask your doctor or nurse about medicine that is available to help stop or lessen loose bowel movements.
  • Drink 6-8 cups of fluids each day unless your doctor has told you to limit your fluid intake due to some other health problem. A cup is 8 ounces of fluid. If you throw up or have loose bowel movements, you should drink more fluids so that you do not become dehydrated (lack water in the body from losing too much fluid).
  • If you get a rash do not put anything on it unless your doctor or nurse says you may. Keep the area around the rash clean and dry. Ask your doctor for medicine if your rash bothers you.

Food and Drug Interactions

There are no known interactions of pembrolizumab with food. This drug may interact with other medications. Tell your doctor and pharmacist about all the medicines and dietary supplements (vitamins, minerals, herbs and others) that you are taking at this time. The safety and use of dietary supplements and alternative diets are often not known. Using these might affect your cancer or interfere with your treatment. Until more is known, you should not use dietary supplements or alternative diets without your cancer doctor's help.

When to Call the Doctor

Call your doctor or nurse right away if you have any of these symptoms: 

  • Fever of 100.5 F (38 C) or higher
  • Chills
  • Easy bleeding or bruising
  • Wheezing or trouble breathing
  • Rash or itching
  • Feeling dizzy or lightheaded
  • Loose bowel movements (diarrhea) more than 4 times a day or diarrhea with weakness or lightheadedness
  • Nausea that stops you from eating or drinking
  • Signs of liver problems: dark urine, pale bowel movements, bad stomach pain, feeling very tired and weak, unusual itching, or yellowing of the eyes or skin

Call your doctor or nurse as soon as possible if any of these symptoms happen:

  • Decreased urine
  • Unusual thirst or passing urine often
  • Nausea that is not relieved by prescribed medicines
  • Rash that is not relieved by prescribed medicines
  • Lasting loss of appetite or rapid weight loss of five pounds in a week
  • Fatigue that interferes with your daily activities
  • Painful, red, or swollen areas on your hands or feet
  • No bowel movement for 3 days or you feel uncomfortable
  • Extreme weakness that interferes with normal activities

Reproduction Concerns

  • Pregnancy warning: This drug may have harmful effects on the unborn child, so effective methods of birth control should be used during your cancer treatment and for at least 4 months after treatment.  Genetic counseling is available for you to talk about the effects of this drug therapy on future pregnancies. Also, a genetic counselor can look at the possible risk of problems in the unborn baby due to this medicine if an exposure happens during pregnancy
  • Breastfeeding warning:  It is not known if this drug passes into breast milk.  For this reason, women should talk to their doctor about the risks and benefits of breast feeding during treatment with this drug because this drug may enter the breast milk and badly harm a breast feeding baby.

New: September 2014

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