Pembrolizumab is used to treat cancer. It works by changing the action of your own immune system, directing it to attack cancer cells. Pembrolizumab belongs to a class of drugs known as monoclonal antibodies.

Read the Medication Guide provided by your pharmacist before you start receiving pembrolizumab and each time you get a treatment. If you have any questions, ask your doctor or pharmacist.

This medication is given by a health care professional. It is injected slowly into a vein over 30 minutes. It is given as directed by your doctor, usually once every 3 weeks or once every 6 weeks. The dosage is based on your medical condition and response to treatment. Children's dosage is also based on weight.

Infusion reactions may happen during the infusion of this drug. Tell your doctor right away if you have any symptoms of infusion reactions such as fever, chills, shaking, flushing, shortness of breath, dizziness, or feeling faint. Your doctor may slow down or stop your treatment for some time.

Use this medication regularly to get the most benefit from it. To help you remember, mark your calendar with a reminder.

See also How to Use section.

Tiredness, swelling ankles/feet/hands, itchy skin, nausea, vomiting, abdominal pain, or trouble sleeping may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

People using this medication may have serious side effects. Some of these effects may occur even after stopping treatment. However, you have been prescribed this drug because your doctor has judged that the benefit to you is greater than the risk of side effects. Careful monitoring by your doctor may decrease your risk.

Tell your doctor right away if you have any serious side effects, including:

• headache that is unusual or doesn't go away
• new/worsening cough
• shortness of breath
• diarrhea with blood/mucus
• symptoms of liver disease (such as nausea/vomiting that doesn't stop, loss of appetite, stomach/abdominal pain, yellowing eyes/skin, dark urine)
• signs of kidney problems (such as change in the amount of urine, pink/bloody urine)
• dizziness/fainting
• vision changes
• deepening of the voice
• eye redness/pain
• sensitivity to light
• numbness/tingling of the arms/legs
• joint stiffness/pain
• muscle weakness/tenderness/pain
• signs of infection (such as sore throat that doesn't go away, fever, chills, burning/painful/frequent/urgent urination)
• easy bruising/bleeding

Pembrolizumab may cause hormone gland problems (such as thyroid, pituitary, adrenal, pancreas). Your body could make too much or too little hormone. Tell your doctor right away if you have any symptoms such as:

• cold or heat intolerance
• unexplained weight loss/gain
• mental/mood changes
• slow/fast/pounding/irregular heartbeat
• unusual tiredness
• constipation

This medication may rarely make your blood sugar rise, which can cause or worsen diabetes. Tell your doctor right away if you have symptoms of high blood sugar such as increased thirst/urination. If you already have diabetes, check your blood sugar regularly as directed and share the results with your doctor. Your doctor may need to adjust your diabetes medication, exercise program, or diet.

Get medical help right away if you have any very serious side effects, including:

• chest pain
• seizure

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before using pembrolizumab, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• organ/tissue transplant

People who receive a donor stem cell transplant after treatment with pembrolizumab may have very serious (possibly fatal) complications. Ask your doctor for more details.

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while using pembrolizumab. Pembrolizumab may harm an unborn baby. Ask about reliable forms of birth control while using this medication and for 4 months after the last dose. If you become pregnant, talk to your doctor right away about the risks and benefits of this medication.

It is unknown if this drug passes into breast milk. Because of the possible risk to the infant, breastfeeding is not recommended while using this drug and for 4 months after the last dose. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669.

Lab and/or medical tests (such as liver/kidney/thyroid function, blood sugar, complete blood count) should be done before and during treatment with this medication. Keep all medical and lab appointments. Consult your doctor for more details.

It is important to get each dose of this medication as scheduled. If you miss a dose, ask your doctor or pharmacist right away for a new dosing schedule.

Not applicable. This medication is given in a hospital or clinic and will not be stored at home.