Can Keytruda (pembrolizumab) cause diarrhea?
Yes. Diarrhea is a known possible side effect of Keytruda (pembrolizumab), including as part of immune-related inflammation of the gut called colitis. This can range from mild loose stools to more severe diarrhea that may require medical treatment. [1]
When does Keytruda diarrhea happen?
Diarrhea can occur at any time during treatment, but immune-related side effects often show up after starting therapy and can also develop later. If diarrhea starts or worsens, it should be treated as potentially immune-related until proven otherwise. [1]
What symptoms suggest Keytruda-related colitis?
Patients and caregivers are typically advised to watch for diarrhea that is persistent or severe, and for signs of worsening gut inflammation such as:
- More frequent or watery stools
- Abdominal pain or cramping
- Blood or mucus in stool
- Fever or feeling very unwell
These symptoms increase the need for urgent medical evaluation while on Keytruda. [1]
What should I do if I get diarrhea while on Keytruda?
Contact your oncology care team promptly. Do not try to “wait it out” if symptoms are significant, because immune-related colitis sometimes requires prescription treatment (often corticosteroids) and guidance on holding or continuing Keytruda. [1]
How is Keytruda diarrhea different from common stomach bugs?
Many causes of diarrhea are possible (foodborne illness, infection, other medications), but on Keytruda, diarrhea also has an immune-related cause that needs assessment. Clinicians consider severity, timing, and other symptoms to decide whether it is likely drug-related colitis versus an infection. [1]
Is diarrhea more likely with other cancer immunotherapies?
Diarrhea/colitis can also occur with other immune checkpoint inhibitors (because they can similarly trigger immune-related inflammation). The Keytruda label specifically documents diarrhea as a possible side effect, including immune-related gastrointestinal events. [1]
Source
- Drug label information for Keytruda (pembrolizumab) – diarrhea/colitis side effects