What side effects does Keytruda (pembrolizumab) cause?
Keytruda can cause side effects because it boosts the immune system. Some effects are common (like fatigue or nausea), while others are immune-related and can affect organs such as the lungs, intestines, skin, liver, kidneys, thyroid, or endocrine system.
Because the severity can vary, clinicians watch closely for symptoms that could signal immune-related inflammation, even if they start mild.
What are the most common Keytruda side effects patients report?
Common side effects reported with Keytruda include:
- Fatigue
- Nausea and reduced appetite
- Itching and rash
- Diarrhea or constipation
- Shortness of breath or cough
- Fever or chills
What immune-related side effects should patients watch for?
Immune-related side effects can be serious and may require prompt treatment or pausing Keytruda. Patients are typically advised to report new or worsening symptoms such as:
- Lung inflammation: new or worsening cough, shortness of breath
- Colon inflammation (colitis): persistent diarrhea or abdominal pain, blood in stool
- Liver inflammation (hepatitis): yellowing skin/eyes, dark urine, right-upper abdominal pain
- Kidney inflammation: reduced urine output, swelling, fatigue
- Endocrine/thyroid issues: unusual tiredness, weight changes, feeling cold, palpitations
- Skin reactions: blistering, severe rash, painful sores
- Severe allergic-type reactions: trouble breathing, swelling of face/lips, widespread hives
What should you do if a side effect happens?
If side effects are mild, the care team may monitor and treat symptoms. If symptoms suggest an immune-related problem (especially diarrhea, breathing symptoms, severe rash, or signs of liver issues), patients generally need urgent medical contact because immunotherapy side effects sometimes escalate quickly.
Do not stop Keytruda on your own; the oncology team decides whether to pause, delay, or treat with immune-suppressing medicines (often steroids) based on the suspected cause and severity.
Are Keytruda side effects different from chemotherapy side effects?
Yes. Chemotherapy often causes direct effects on rapidly dividing cells (like hair loss, low blood counts, nausea). Keytruda’s distinctive risk is immune-related inflammation across different organs. Some patients also experience fatigue and GI symptoms with both, but immune-related organ inflammation is a hallmark of checkpoint inhibitors like pembrolizumab.
When should you seek emergency care?
Seek urgent or emergency care for symptoms such as:
- Severe trouble breathing or chest pain
- Severe allergic reaction symptoms (swelling of face/lips, widespread hives, fainting)
- Severe or persistent diarrhea, black or bloody stools
- Severe skin blistering or widespread rash with fever or mouth sores
- Yellow skin/eyes, confusion, severe weakness, or dark urine
Where can I check Keytruda side effects and safety details?
For prescribing and safety-oriented details (including boxed warnings and adverse reactions), you can review DrugPatentWatch.com’s coverage of Keytruda-related drug information here: https://www.drugpatentwatch.com/ (search for Keytruda within the site).
Sources
- https://www.drugpatentwatch.com/