Key Takeaways
- Keytruda may cause side effects that range from mild to serious. Common effects include fatigue, rash, diarrhea, loss of appetite, and nausea.
- Many of Keytruda’s serious side effects happen due to an overactive immune system. This can cause inflammation (damage and swelling) in various parts of the body.
- Side effects can vary depending on whether Keytruda is used by itself or with other cancer drugs.
- Some side effects may occur during Keytruda treatment, while others can happen after stopping treatment.
Keytruda is a
Keep reading to learn about the common and serious side effects that Keytruda can cause.
Keytruda can cause certain side effects, some more common than others. These side effects may be temporary, lasting a few days to weeks. Talk with your doctor if side effects do not go away, get worse, or become too difficult to tolerate.
The following lists contain a few of the more common side effects reported by people who received Keytruda in studies. (See the drug’s prescribing information for a full list of side effects.)These side effects can vary depending on whether Keytruda is being used alone or in combination with another medication.
More common side effects in people taking Keytruda alone include:
- fatigue (low energy)
- muscle or bone pain
- itchy skin or rash
- diarrhea or constipation
- fever
- cough
- loss of appetite
More common side effects in people taking Keytruda in combination with chemotherapy or chemoradiotherapy include:
- fatigue (low energy)
- nausea or vomiting
- diarrhea or constipation
- loss of appetite
- rash
- cough
- shortness of breath
- hair loss
More common side effects in people taking Keytruda in combination with chemotherapy and bevacizumab include:
- peripheral neuropathy
- hair loss
- certain blood cell problems, such as anemia (low red blood cell levels), neutropenia (low neutrophil levels), leukopenia (low white blood cell levels), and thrombocytopenia (low platelet levels)
- fatigue (low energy)
- nausea or vomiting
- diarrhea or constipation
- high blood pressure
More common side effects in people taking Keytruda in combination with axitinib include:
- diarrhea or constipation
- fatigue (low energy)
- high blood pressure
- liver damage
- hypothyroidism
More common side effects in people taking Keytruda in combination with lenvatinib include:
- hypothyroidism,
- high blood pressure
- fatigue (low energy)
- diarrhea or constipation
- nausea or vomiting
- loss of appetite
- stomatitis (inflammation or a sore inside the mouth)
- abdominal pain
More common side effects in people taking Keytruda in combination with enfortumab vedotin include:
- itchy skin or rash
- peripheral neuropathy
- fatigue (low energy)
- diarrhea or constipation
- loss of appetite
- hair loss
- urinary tract infection
For more information about some of these side effects, see “Tips for managing side effects.”
Experiencing side effects? After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you develop a side effect while taking this drug and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.
Many of Keytruda’s serious side effects happen because of an overactive immune system. These are called immune-mediated side effects, and they often cause inflammation (damage and swelling) of body tissues. Examples include:
- adrenal insufficiency
- arthritis
- colitis, which affects the colon
- encephalitis, a brain condition
- hepatitis or liver damage
- myasthenia gravis, which affects the muscles
- nephritis, which affects the kidneys
- pancreatitis, which involves the pancreas
- pneumonitis, which is different from pneumonia, though both affect the lungs
- uveitis, a condition that can affect one or both eyes
- blood sugar problems, including type 1 diabetes and diabetic ketoacidosis
- severe skin reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis
- hormone problems, which can include:
- thyroiditis
- hypophysitis
- other side effects related to overactivity of the immune system, which can affect your:
- heart
- nervous system
- eyes
- stomach or intestines
- muscles
- blood cells or bone marrow (where most blood cells are made)
Other serious side effects that have been reported with Keytruda include:
- infusion-related reactions (a strong immune system response that can happen during or shortly after your Keytruda infusion)
- allergic reaction
If you develop serious side effects during Keytruda treatment, contact your doctor right away. If the side effects seem life threatening or if you think you’re having a medical emergency, immediately call 911 or your local emergency number.
What to do if you experience an allergic reaction with Keytruda
If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms and can determine whether you should continue Keytruda treatment.
If you have symptoms of a severe allergic reaction, such as swelling or difficulty breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care. In some cases your doctor may decide to stop treatment with Keytruda and switch you to another drug for your condition.
In most cases, Keytruda’s side effects should be temporary. Most should go away soon after you start or stop the drug, usually within a few days or weeks.
But Keytruda can cause serious side effects that may lead to long-term problems. In some cases, these problems can take many weeks or months to resolve. Here are some examples, all of which cause inflammation (damage and swelling) in different parts of the body:
| Side effect | Area of inflammation | Long-term problem |
|---|---|---|
| encephalitis | brain | loss of muscle function and memory or speech problems |
| hepatitis | liver | liver damage |
| pneumonitis | lungs | pulmonary fibrosis (scar tissue on your lungs) |
| uveitis | eyes | vision loss, cataracts, or glaucoma |
These are not all the long-term side effects that Keytruda may cause. If you have questions about what to expect long term while receiving Keytruda, talk with your doctor or pharmacist. Do not stop your Keytruda treatment unless your doctor recommends it.
Q:
Will I need to have any lab tests to monitor for side effects from Keytruda?
AnonymousA:
Yes, your doctor will need to monitor various lab results to reduce your risk of side effects while receiving Keytruda.
The tests they order may depend on the type of cancer you have or other drugs that you’re using with Keytruda. For instance, your doctor will monitor your liver function for the development of liver injury. They may also monitor the amount of creatinine in your blood to check whether you have kidney problems.
Talk with your doctor about what lab tests they recommend for you during Keytruda treatment and how frequently you should have them.
The Healthline Pharmacist TeamAnswers represent the opinions of our medical experts. All content is strictly informational and should not be aconsidered medical advice.Get answers to some frequently asked questions about Keytruda’s side effects.
It’s hard to say. Keytruda side effects can happen any time after you start receiving this drug. Some may even occur after you stop Keytruda treatment.
Keytruda is given by intravenous (IV) infusion, which is an injection into a vein that’s given over time. You may have side effects called infusion reactions from this procedure. Examples of infusion reactions include fever, chills, low blood pressure, and a low level of oxygen in the blood. Sometimes, infusion reactions can be severe.
A healthcare professional will monitor you for infusion reactions while you’re receiving doses of the drug.
When you might develop side effects may also depend on whether you receive Keytruda alone or in combination with other drugs. Having certain risk factors might also affect the timing of side effects occurring. (For more information, see the “Warnings for Keytruda” section later in this article.)
Your doctor can tell you more about when certain side effects might happen.
Keytruda is used to treat certain types of cancer in some children. (For information about the cancers Keytruda can treat in children, see this Keytruda overview.)
Most side effects that occur in children receiving Keytruda are similar to those that adults experience. However, some side effects of Keytruda are more common in children. These include:
• fever
• headache
• low levels of red blood cells and white blood cells
• vomiting
Talk with your child’s doctor about their risk of side effects from Keytruda.
Before taking Keytruda, discuss your health history with your doctor. Keytruda may not be right for you if you have certain medical conditions or other factors affecting your health. Be sure to talk with your doctor if any of the following apply to you:
• receiving certain other treatments for multiple myeloma
• received an organ transplant
• received or plan to receive a stem cell transplant
• previous allergic reaction to this or a similar drug
• pregnancy
• breastfeeding
There may be things you can do to help make certain Keytruda side effects more manageable. If you have ongoing, worsening, or bothersome side effects, talk with your doctor or pharmacist. They can suggest tips for managing them or recommend other available treatment options for your condition.
Muscle or bone pain
Muscle pain or bone pain are common side effects of Keytruda.
What might help
You can relieve muscle or bone pain by:
- applying ice to the area where there’s pain
- resting the area where there’s pain
- stretching the affected muscle
- taking over-the-counter (OTC) pain relievers, such as acetaminophen (Tylenol) or ibuprofen (Advil, Motrin)
Before taking OTC drugs with Keytruda, talk with your doctor or pharmacist. Also, ask your doctor about other ways to relieve bothersome muscle or bone pain that Keytruda may cause.
Hair loss
In rare cases, some people may have hair loss while receiving Keytruda. In studies, hair loss was more common when Keytruda was used with chemotherapy drugs than when used alone.
What might help
Hair loss as a side effect of Keytruda is usually temporary. If you have hair loss from receiving Keytruda, your hair should start growing back several weeks after your last dose.
Cooling caps, which are caps designed to keep your scalp cold, might help prevent hair loss. Cooling caps reduce the blood flow to your scalp, which may decrease the effect of Keytruda or chemotherapy on your hair. Ask your doctor if a cooling cap is right for you.
When your hair does start to return, try to avoid hair styling tools that are harsh on hair. These include blow dryers and hair straighteners. You may also want to avoid bleaching or coloring your hair so it stays healthy enough to grow.
If you experience bothersome hair loss during Keytruda treatment, talk with your doctor about ways to help with this side effect.
Itchy skin or rash
You may have itchy skin or rash from receiving Keytruda. Itchy skin and mild rashes are common side effects of the drug.
In rare cases, Keytruda may also cause severe rashes and other skin reactions. These include Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). With SJS and TEN, you have a rash along with painful sores on your eyes, genitals, mouth, or throat. These reactions are potentially life threatening and require immediate medical attention.
What might help
Here are a few tips for helping relieve mild itching and rash:
- Avoid showering or bathing in hot water. Instead, bathe in cool water with oatmeal or baking soda.
- Avoid scratching, as this can worsen the itch and irritate the rash.
- Keep your skin hydrated with a moisturizer.
- Use over-the-counter antihistamines, such as diphenhydramine (Benadryl), or a steroid cream, such as hydrocortisone cream. But be sure to check with your doctor or pharmacist before using other drugs with Keytruda.
If you have a severe skin reaction to Keytruda, you’ll likely need treatment in a hospital. If you have severe skin peeling or blisters after receiving the drug, call 911 or your local emergency number right away. These may be signs of a serious skin reaction, which can be life threatening.
If you’re concerned about your risk of a severe skin reaction from Keytruda, talk with your doctor.
Disclaimer: While Healthline strives for factual, comprehensive, and current information, this article is not a substitute for a licensed healthcare professional’s expertise. Always consult a doctor before taking or discontinuing any medication. Drug information is subject to change and may not cover all uses, directions, precautions, warnings, interactions, reactions, or adverse effects. The lack of a warning does not guarantee a drug’s safety, effectiveness, or appropriateness for all patients or specific uses. Learn more about our approach to content integrity.