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Keytruda

pembrolizumab
Used for Bladder Cancer, Breast Cancer, Cervical Cancer, Colon Cancer, Esophageal Cancer, Hodgkin Lymphoma, Liver Cancer, Lung Cancer, Melanoma, Mesothelioma, Non-Hodgkin Lymphoma, Ovarian Cancer, Renal Cancer, Skin Cancer, Stomach Cancer, Uterine Cancer

Keytruda (pembrolizumab) is an immunotherapy medication. It helps treat many different kinds of cancer. This can include lung cancer, breast cancer, and melanoma. It works as a PD-1 inhibitor to turn on your immune system and help it attack the cancer better. Keytruda (pembrolizumab) is given as an infusion through the vein at a medical center or clinic. It's given either every 3 weeks or every 6 weeks, depending on your treatment plan. Side effects can include tiredness, diarrhea, rash, and trouble breathing. Your cancer treatment might be just Keytruda (pembrolizumab), or it might be given with other cancer therapies.

Reviewed by:
reviewerAllison Baxley, PharmD, BCOP
reviewerCydnee Ng, PharmD
Last reviewed on February 19, 2026
basics-icon

What is Keytruda (pembrolizumab)?

What is Keytruda (pembrolizumab) used for?

Certain types of:

How Keytruda (pembrolizumab) works

Keytruda (pembrolizumab) is an immunotherapy medication. More specifically, it's a programmed death-1 inhibitor, or PD-1 inhibitor. It’s also called a checkpoint inhibitor.

Keytruda (pembrolizumab) works by blocking the programmed death-1 (PD-1) pathway. This is important because some cancer cells use the PD-1 pathway to hide from the immune system. When this happens, the immune system can’t find and attack the cancer cells as well. And so, the cancer can grow.

By blocking the PD-1 pathway, Keytruda (pembrolizumab) helps the immune system find cancer cells and destroy them better. This helps stop the cancer from growing.

Drug facts

Common BrandsKeytruda
Drug ClassPD-1 inhibitor
Controlled Substance ClassificationNot a controlled medication
Generic StatusNo lower-cost generic available
AvailabilityPrescription only
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Side effects of Keytruda (pembrolizumab)

The following side effects may get better over time as your body gets used to the medication. Let your healthcare provider know immediately if you continue to experience these symptoms or if they worsen over time.

Common Side Effects

Less Common Side Effects

Note: Side effects were from adults with non-small cell lung cancer who took Keytruda (pembrolizumab) by itself. It can be different when treating a different cancer and when taken with other cancer therapies. It can also be different for children.

Keytruda (pembrolizumab) serious side effects

Contact your healthcare provider immediately if you experience any of the following.

  • Serious immune-related side effects: rash, diarrhea, trouble breathing, chest pain, severe stomach pain, mucus or blood in stool
  • Serious reaction during infusion: chills, fever, itching, fast heartbeat, trouble breathing
When do Keytruda (pembrolizumab) possible side effects begin and end?
Time passed since treatment started:
H
D
W
M
Rash or itchiness
Diarrhea
Thyroid problems
Seek immediate medical care if you experience this side effect.
If a line continues to the right, you'll likely keep experiencing this side effect once it starts.

Source: FDA

The following Keytruda (pembrolizumab) side effects have also been reported

Side effects that you should report to your care team as soon as possible:

  • Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
  • Dry cough, shortness of breath or trouble breathing
  • Eye pain, redness, irritation, or discharge with blurry or decreased vision
  • Heart muscle inflammation—unusual weakness or fatigue, shortness of breath, chest pain, fast or irregular heartbeat, dizziness, swelling of the ankles, feet, or hands
  • Hormone gland problems—headache, sensitivity to light, unusual weakness or fatigue, dizziness, fast or irregular heartbeat, increased sensitivity to cold or heat, excessive sweating, constipation, hair loss, increased thirst or amount of urine, tremors or shaking, irritability
  • Infusion reactions—chest pain, shortness of breath or trouble breathing, feeling faint or lightheaded
  • Kidney injury (glomerulonephritis)—decrease in the amount of urine, red or dark brown urine, foamy or bubbly urine, swelling of the ankles, hands, or feet
  • Liver injury—right upper belly pain, loss of appetite, nausea, light-colored stool, dark yellow or brown urine, yellowing skin or eyes, unusual weakness or fatigue
  • Pain, tingling, or numbness in the hands or feet, muscle weakness, change in vision, confusion or trouble speaking, loss of balance or coordination, trouble walking, seizures
  • Rash, fever, and swollen lymph nodes
  • Redness, blistering, peeling, or loosening of the skin, including inside the mouth
  • Sudden or severe stomach pain, bloody diarrhea, fever, nausea, vomiting

Side effects that usually do not require medical attention (report to your care team if they continue or are bothersome):

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Pros and cons of Keytruda (pembrolizumab)

Pros

  • Recommended first-choice treatment for many types of cancers under certain situations
  • Given every 3 or 6 weeks, depending on the treatment plan
  • Less likely to cause nausea, vomiting, and hair loss than traditional chemotherapy

Cons

  • Given as an injection through the vein
  • Might cause immune-related side effects like diarrhea, rash, and lung problems
  • Might need to take a break from treatment and take a corticosteroid to manage some side effects
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Pharmacist tips for Keytruda (pembrolizumab)

pharmacist
  • Put your infusion appointments on your calendar to help you remember when they are. Keytruda (pembrolizumab) infusions are every 3 weeks or every 6 weeks. This depends on your specific treatment plan. If you miss an appointment, call the medical office as soon as you can to reschedule.
  • Each Keytruda (pembrolizumab) infusion takes at least 30 minutes. It could take longer than this, since you'll need to check in and get settled. Plan enough time for your appointments and bring something to do to pass the time. Examples include bringing a book to read or an electronic device to watch something.
  • Get your lab tests done on time while you’re taking Keytruda (pembrolizumab). These labs help your oncology care team check for possible side effects you might not feel at first. They can include liver, kidney, or thyroid problems, among others.
  • Tell your oncology team right away if you have any immune-related side effects at any time while taking Keytruda (pembrolizumab). These side effects can include diarrhea, rash, or trouble breathing. You might need extra medical care to help with these side effects. Depending on how severe it is, your oncologist will decide if you should keep taking the medication, take a short break, or stop taking it completely.
  • Don’t take any over-the-counter (OTC) medications for side effects from Keytruda (pembrolizumab) without checking with your oncology team first. OTC medications, like loperamide (Imodium A-D) for diarrhea, might not work well enough. You might need a steroid or other supportive medications to help you feel better.
  • If you need to take a steroid for a few weeks to help with side effects, don’t suddenly stop taking it. If you do, you might have uncomfortable symptoms like body aches or stomach cramps. Your care team will give you specific instructions to taper the steroid, or slowly lower the dose, to stop.
  • If you have diarrhea while taking Keytruda (pembrolizumab), drink lots of fluids, like soup broth or electrolyte drinks. This helps prevent dehydration. Also eat foods that are easier on your stomach, like bananas, rice, and toast. Avoid greasy or fried foods, dairy products, and too much fiber. Also don't drink alcohol, caffeinated drinks (like coffee), and sugary beverages. They can make diarrhea worse. If you have diarrhea, tell your oncology care team so they can give you tips to feel better.
  • Although it's rare, you might have a reaction during your Keytruda (pembrolizumab) infusion. Tell the nurse right away if you have chills, trouble breathing, itching, rash, or fever. Your care team can help manage the reaction quickly.
  • If you can get pregnant, use reliable birth control if you're having sex while taking Keytruda (pembrolizumab). Keep using birth control for another 4 months after you stop Keytruda (pembrolizumab). This medication might harm an unborn baby. Let your care team know right away if you become pregnant during treatment.
  • Don’t breastfeed while you’re taking Keytruda (pembrolizumab) and for 4 months after your last dose. We don’t know if the medication can get into breast milk. But there's a potential risk that it can and harm your baby. So, it might be safer to find alternative feeding options. Talk to your prescriber or a lactation specialist about other options.
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Risks and warnings for Keytruda (pembrolizumab)

Keytruda (pembrolizumab) can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.

Immune-related side effects

Immunotherapy medications like Keytruda (pembrolizumab) can cause immune-related adverse events (irAEs). These side effects happen when your immune system becomes too active. It causes your immune system to start attacking healthy cells, not just cancer cells.

These side effects can happen anywhere in your body and at any time while you're taking Keytruda (pembrolizumab). They can be mild or very serious.

Some side effects show up on your lab test results. These include liver or kidney problems. That's why it's important to get your blood work done on time, even if you feel fine. This helps your care team check for any side effects that you can't easily spot.

Other side effects can cause symptoms you can feel. Examples include diarrhea, rash, and trouble breathing. Tell your care team right away if you notice these symptoms or anything unusual. Depending on how severe your symptoms are, you might need to stop Keytruda (pembrolizumab) for a while and take a steroid to help you feel better.

Infusion-related reactions

Although rare, people who take Keytruda (pembrolizumab) can have reactions during the infusion. This can include anaphylaxis. Reactions can be mild to severe and sometimes even life-threatening.

The nurse will watch for reactions during your Keytruda (pembrolizumab) infusion. But tell them right away if you have chills, trouble breathing, flushing, itchiness, rash, or fever while you're getting the infusion.

Most of the time, pausing or slowing the infusion can help manage these infusion reactions. Then, you can keep taking Keytruda (pembrolizumab). But if the reaction is severe, you might need to stop the medication altogether.

Complications from stem cell transplants

  • Risk factors: People who’ve had a stem cell (bone marrow) transplant

Some people who’ve taken medications like Keytruda (pembrolizumab) and have had a stem cell transplant can have serious problems. This can include liver damage called veno-occlusive disease (VOD). It can also lead to graft-versus-host disease (GVHD).

Before starting Keytruda (pembrolizumab), tell your oncology team if you’ve had a stem cell transplant. Also tell them if you have one planned at any time after you're done with Keytruda (pembrolizumab). Your care team will follow up with you often to check for signs of these problems.

Harm to an unborn baby

  • Risk factors: Pregnancy

Based on animal studies and the way Keytruda (pembrolizumab) works, it might harm an unborn baby if it's given during pregnancy.

If you can get pregnant, your oncologist might ask you to take a pregnancy test before you start treatment. This double checks you're not pregnant before starting Keytruda (pembrolizumab).

Once you start Keytruda (pembrolizumab), use reliable birth control if you're having sex. Keep using birth control for 4 more months after your last dose. Tell your care team right away if you get pregnant at any time during treatment.

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Keytruda (pembrolizumab) dosage

Typical dosage for Keytruda (pembrolizumab)

Keytruda (pembrolizumab) is given as an infusion in the vein. This is called an intravenous (IV) infusion. It's given by a trained healthcare professional at a medical center or infusion clinic.

Your dose depends on your treatment plan.

  • Adults: The typical dose is either 200 mg given IV once every 3 weeks OR 400 mg given IV once every 6 weeks. Depending on your cancer, you either take Keytruda (pembrolizumab) by itself or with other cancer therapies.

  • Children (for certain cancers only): The prescriber will find the dose based on your child's body weight (in kilograms, kg). The typical dose is 2 mg/kg (up to a maximum of 200 mg). It's given IV once every 3 weeks.

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What are alternatives to Keytruda (pembrolizumab)?

There are a number of medications that your doctor can prescribe in place of Keytruda (pembrolizumab). Compare a few possible alternatives below.
Keytruda (pembrolizumab)
Used for:

Certain types of:

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Used for:
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Used for:

Certain types of:

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News about Keytruda (pembrolizumab)

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Keytruda (pembrolizumab) images

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References

Best studies we found

American Cancer Society. (2024). Infusion or immune reactions.

American Cancer Society. (2024). Hair loss (alopecia).

American Cancer Society. (2025). Chemotherapy.

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