Pembrolizumab
Pronunciation: pem-broh-LIZ-oo-mab.
- Generic name
- pembrolizumab
- Drug class
- PD-1 (programmed death receptor-1) blocking monoclonal antibody -- a type of immune checkpoint inhibitor
- Form
- Concentrate for solution for infusion / solution for injection
- Route
- Intravenous infusion (some markets also offer a subcutaneous injection form)
- Legal status
- Prescription-only, administered by a healthcare professional
Availability and supply rules vary by country
Trade names by country: United States · United Kingdom · Canada · Australia · New Zealand
Australia: Keytruda (5) · Full directory
What pembrolizumab is and how it works
Pembrolizumab is a prescription cancer immunotherapy medicine given by a healthcare professional, usually as an intravenous infusion (a subcutaneous injection form is also available in some markets). It works by blocking PD-1, a protein that can otherwise stop the immune system from attacking cancer cells, so the immune system can recognise and fight the cancer more effectively. (1)
Pembrolizumab is given to you by a cancer care team, usually every few weeks, as part of a treatment plan specific to your type and stage of cancer. Because it works through your immune system, it can occasionally cause your immune system to attack healthy parts of the body -- your care team will explain what symptoms to watch for and monitor you with regular blood tests.
Mechanism of action: how pembrolizumab works
Pembrolizumab is a humanised IgG4/kappa monoclonal antibody (with a stabilising Fc-region alteration) that binds the PD-1 receptor on T cells, blocking its interaction with the ligands PD-L1 and PD-L2. This removes an inhibitory 'checkpoint' signal that some tumours exploit to evade immune attack, restoring T-cell-mediated anti-tumour immune activity -- which is also the mechanism behind its characteristic immune-mediated adverse reactions. (1) (3)
What pembrolizumab is used for
A wide range of cancers, used alone or combined with other treatments
Pembrolizumab is approved for many different types of cancer, including certain melanomas, non-small cell lung cancer, head and neck cancer, classical Hodgkin lymphoma, urothelial (bladder-type) cancer, oesophageal and gastric cancers, cervical cancer, kidney cancer, endometrial cancer, triple-negative breast cancer, and some tumours identified by specific genetic features (such as MSI-H, dMMR, or high tumour mutational burden), regardless of where in the body the cancer started. Your oncologist will confirm whether your specific cancer type and stage is an approved use, and whether it is given alone or combined with chemotherapy or other cancer medicines. (1) (2) (3)
Before taking pembrolizumab
Do not take / not appropriate for
- Do not receive pembrolizumab if you have had a severe allergic reaction to it or any of its ingredients. (all countries) (2)
Tell your clinician about
- Any autoimmune disease (such as Crohn's disease, ulcerative colitis, lupus, or rheumatoid arthritis).
- Any organ transplant, including a stem cell or bone marrow transplant.
- Any lung, liver, kidney, thyroid, or other hormone gland problems.
- All other medicines you take, including steroids and any immune-suppressing medicines.
- Pregnancy, plans for pregnancy, or breastfeeding -- effective contraception is generally needed during treatment and for a period after your last dose.
How to take pembrolizumab
- Given by a healthcare professional as an intravenous infusion (drip) over about 30 minutes, or as a subcutaneous injection where that form is available, typically every 3, 6, or occasionally longer number of weeks depending on your specific treatment plan.
- You will usually be monitored during and after the infusion for reactions.
- Your oncology team carries a patient alert card system in many countries -- carry any card you are given and show it to any other doctor or healthcare professional you see, including in an emergency.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6)
Missed dose
Pembrolizumab is given on a schedule managed by your oncology team, who will reschedule a missed or delayed infusion appointment as clinically appropriate. Contact your cancer care team if you are going to miss a scheduled appointment.
Overdose
Pembrolizumab is administered by a healthcare professional in a monitored setting, so accidental overdose by a patient is not applicable in the way it is for self-administered medicines. If you experience severe or unusual symptoms after an infusion, contact your cancer care team or seek urgent medical attention. (1)
Side effects
Side effects and their urgency vary; report severe, persistent, or concerning symptoms.
Tiredness (fatigue).
What to notice: Tiredness (fatigue).
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)
Muscle or joint pain.
What to notice: Muscle or joint pain.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)
Rash and itching.
What to notice: Rash and itching.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)
Diarrhoea.
What to notice: Diarrhoea.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)
Fever, cough, and reduced appetite.
What to notice: Fever, cough, and reduced appetite.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)
Underactive thyroid (hypothyroidism) -- common enough that thyroid function is checked regularly.
What to notice: Underactive thyroid (hypothyroidism) -- common enough that thyroid function is checked regularly.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1) (2)
When combined with chemotherapy: nausea, constipation, mouth sores, hair loss, and nerve-related symptoms such as tingling or numbness.
What to notice: When combined with chemotherapy: nausea, constipation, mouth sores, hair loss, and nerve-related symptoms such as tingling or numbness.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)
Serious warnings
Signs of lung inflammation (pneumonitis) — emergency
Symptoms: New or worsening cough, chest pain, or shortness of breath.
Action: Contact your cancer care team immediately or seek urgent medical attention -- this reaction can occasionally be fatal if not treated promptly. Your oncology team will decide on monitoring, steroid treatment, and whether to pause or stop pembrolizumab based on severity. (1) (2)
Signs of bowel inflammation (colitis) — high caution
Symptoms: Diarrhoea, more frequent bowel movements than usual, blood or mucus in stool, or severe stomach pain.
Action: Tell your cancer care team promptly. Severe cases can risk bowel perforation, so do not wait for symptoms to resolve on their own -- report them the same day where possible. (1) (2)
Signs of liver inflammation (hepatitis) — high caution
Symptoms: Yellowing of the skin or eyes, dark urine, nausea or vomiting, pain on the right side of the stomach, or unusual tiredness.
Action: Contact your cancer care team promptly -- liver function is checked regularly with blood tests to catch this early. (1)
Signs of hormone gland problems (endocrinopathies -- thyroid, adrenal gland, pituitary gland, or new-onset diabetes) — high caution
Symptoms: Extreme tiredness, unexplained weight change, headache, changes in mood or behaviour, dizziness or fainting, hair loss, feeling cold, constipation, deepening of the voice, excessive thirst or urination, or changes in vision.
Action: Report these to your cancer care team -- hormone levels are checked regularly with blood tests, and hormone replacement treatment can often manage this while you continue pembrolizumab, guided by your care team. (1) (2)
Signs of kidney inflammation (nephritis) — high caution
Symptoms: Decreased urination, blood in urine, swelling in the ankles, or loss of appetite.
Action: Contact your cancer care team -- kidney function is monitored with regular blood tests. (1) (2)
Signs of a severe skin reaction (including rare Stevens-Johnson syndrome or toxic epidermal necrolysis) — emergency
Symptoms: Severe or widespread rash, blistering, peeling skin, or painful sores in the mouth, eyes, or genitals, sometimes with fever.
Action: Seek urgent medical attention immediately -- these reactions can be life-threatening. (1) (2)
Signs of heart inflammation (myocarditis) — emergency
Symptoms: Chest pain, shortness of breath, irregular heartbeat, or severe fatigue.
Action: Seek urgent medical attention immediately -- pembrolizumab is generally permanently stopped by the treating clinician if myocarditis is suspected, given how serious this reaction can be. (1)
Signs of a severe infusion-related reaction — emergency
Symptoms: Fever, chills, flushing, itching, rash, dizziness, wheezing, or swelling of the face/throat during or shortly after an infusion.
Action: Tell the treatment team immediately during your infusion -- they are equipped to slow, pause, or stop the infusion and treat the reaction. Severe reactions lead to permanently stopping pembrolizumab, as decided by your care team. (1) (2)
Complications after a prior stem cell or organ transplant — high caution
Symptoms: New or worsening symptoms after pembrolizumab if you have previously had a stem cell/bone marrow or solid organ transplant -- this can include fever, rash, diarrhoea, or signs of organ rejection.
Action: Make sure your cancer care team knows about any prior transplant before starting treatment, and report any new symptoms promptly -- these complications, including graft-versus-host disease and organ rejection, can be serious or fatal. (1) (2)
Interactions
- No significant pharmacokinetic drug-drug interactions are expected, since pembrolizumab is a large protein (monoclonal antibody) rather than a small-molecule drug metabolised by typical liver enzyme pathways. (2)
- Systemic corticosteroids or other medicines that suppress the immune system are generally avoided before starting pembrolizumab, as they may reduce its effectiveness -- but they are an important part of managing immune-mediated side effects once treatment has started, guided by your care team. (2)
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy
Pembrolizumab can cause harm to an unborn baby based on its mechanism of action. Effective contraception is generally recommended during treatment and for a period after the last dose (4 months, per the US label) -- discuss timing with your oncology team. (1) (2) (3) (4) (5) (6)
Breastfeeding
Breastfeeding is not recommended during treatment with pembrolizumab. (1) (2) (3) (4) (5) (6)
Children
Approved for certain cancer types in adolescents (from around age 12, depending on indication and country) and in some paediatric settings for tumours with specific genetic features -- your oncology team will confirm age-specific approved uses. (1) (2) (3) (4) (5) (6)
Elderly
Used in older adults as part of an individualised cancer treatment plan; no specific separate dosing rules based on age alone are described in the sources reviewed, beyond the usual careful monitoring for all patients. (1) (2) (3) (4) (5) (6)
Hepatic_impairment
Used with caution and closer liver-function monitoring in patients with pre-existing liver problems, given the risk of immune-mediated hepatitis. (1) (2) (3) (4) (5) (6)
Renal_impairment
Used with caution and closer kidney-function monitoring in patients with pre-existing kidney problems, given the risk of immune-mediated nephritis. (1) (2) (3) (4) (5) (6)
Source_ids
US-DAILYMED-KEYTRUDA-2026,UK-EMC-KEYTRUDA-2026 (1) (2) (3) (4) (5) (6)
Monitoring
Before starting
- Liver function tests
- Kidney function (creatinine)
- Thyroid function tests
- Review of autoimmune disease history and any prior transplant
During treatment
- Regular liver, kidney, and thyroid function blood tests throughout treatment.
- Close clinical monitoring for symptoms suggesting immune-mediated reactions in any organ system.
- Monitoring during and shortly after each infusion for infusion-related reactions.
Storage
Stored and handled entirely by pharmacy and clinical staff under refrigeration, protected from light, following the specific product's storage instructions -- this is not a medicine that patients store or handle themselves at home.
Professional information
Clinician-facing context only, sourced from the current US FDA prescribing information and UK/EU SmPC; verify against the current full label and specific indication-based dosing regimen before prescribing.
United States / United Kingdom / European Union
Indication: Multiple approved solid tumour and haematologic malignancy indications, as monotherapy or in combination regimens
Dose summary: Dosing is indication-specific and individualised (commonly weight-based or flat-dose regimens given every 3 or 6 weeks intravenously; a subcutaneous formulation is also available in some markets) -- refer to the current full label for the specific regimen matched to the approved indication being treated.
Renal context: No formal dose adjustment described for renal impairment in the sources reviewed; monitored closely given nephritis risk. (1) (2)
Hepatic guidance
No formal hepatic dose adjustment described in the sources reviewed; closer monitoring is used given the risk of immune-mediated hepatitis.
Overdose note
Not applicable in the usual sense, as pembrolizumab is administered by healthcare professionals in a monitored clinical setting under a fixed schedule. (1) (3)
Frequently asked questions
Is pembrolizumab (Keytruda) available in the US, UK, Europe, Canada, Australia, and New Zealand?
Yes, it is approved and available in all of these regions, across a wide range of approved cancer indications. (1) (3) (2) (4) (5) (6)
Why does pembrolizumab affect organs other than the cancer being treated?
Pembrolizumab works by releasing a 'brake' on your immune system so it can attack cancer cells more effectively. The same released immune activity can occasionally also target healthy tissue -- lungs, bowel, liver, hormone glands, kidneys, skin, or heart -- causing immune-mediated side effects. This is why regular monitoring and prompt symptom reporting matter throughout treatment. (1)
What should I do if I notice a new symptom while on pembrolizumab?
Contact your cancer care team promptly, even for symptoms that seem minor, such as mild diarrhoea, a new rash, or unusual tiredness. Many immune-mediated side effects are manageable if caught early -- your care team will assess severity and decide on any treatment changes. (1) (2)
What is the mechanism of action of pembrolizumab?
Pembrolizumab is a humanised IgG4/kappa monoclonal antibody (with a stabilising Fc-region alteration) that binds the PD-1 receptor on T cells, blocking its interaction with the ligands PD-L1 and PD-L2. This removes an inhibitory 'checkpoint' signal that some tumours exploit to evade immune attack, restoring T-cell-mediated anti-tumour immune activity -- which is also the mechanism behind its characteristic immune-mediated adverse reactions. (1) (3)
References
- KEYTRUDA (pembrolizumab) injection -- full prescribing informationU.S. Food and Drug Administration / DailyMed (NIH), full prescribing information, Merck Sharp & Dohme LLC · United States · accessed 2026-07-29 · source 1
- KEYTRUDA 25 mg/mL concentrate for solution for infusion -- Summary of Product Characteristicselectronic medicines compendium (emc), United Kingdom -- Merck Sharp & Dohme (UK) Limited · United Kingdom · accessed 2026-07-29 · source 2
- Keytruda (pembrolizumab) -- EPAR product informationEuropean Medicines Agency (EMA) · European Union · accessed 2026-07-29 · source 3
- KEYTRUDA (pembrolizumab) Product MonographHealth Canada product monograph · Canada · accessed 2026-07-29 · source 4
- KEYTRUDA pembrolizumab -- ARTG registrationTherapeutic Goods Administration (TGA), Australia · Australia · accessed 2026-07-29 · source 5
- Keytruda New Zealand Data SheetMedsafe (New Zealand regulator) · New Zealand · accessed 2026-07-29 · source 6
Brand names by country
Single-ingredient pembrolizumab names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
United States
- KEYTRUDA25 mg/mL · merck sharp & dohme llc
United Kingdom
- Keytruda (2)MHRA licensed emc smpc confirmed · 25 mg/mL concentrate, 395 mg, 790 mg solution for injection · Merck Sharp & Dohme (UK) Limited
Canada
- KEYTRUDA
Australia
- Keytruda (5)TGA ARTG registered 2016-03-08 confirmed · 100 mg/4 mL, KEYTRUDA SC 790 mg/4.8 mL · Merck Sharp & Dohme (Australia) Pty Ltd
New Zealand
- Keytruda (6)Medsafe datasheet confirmed · not specified in confirmed source · Merck Sharp & Dohme (New Zealand) Limited
View brands in additional countries.
European Union
Keytruda (3)