What side effects are most common with Keytruda (pembrolizumab)?
Keytruda (pembrolizumab) can cause side effects in many parts of the body. Commonly reported effects include fatigue and flu-like symptoms, along with diarrhea or constipation and nausea. People also report decreased appetite and skin reactions such as rash or itching. Some patients develop lab changes (for example, issues related to liver tests, thyroid function, or blood counts) that are detected during treatment.
A major feature of Keytruda is immune-related side effects. These can involve organs such as the lungs, liver, colon (bowel), kidneys, endocrine glands (like the thyroid), and skin. These effects may start during treatment or after Keytruda is stopped.
What are the serious immune-related side effects to watch for?
Because Keytruda works by stimulating the immune system, it can trigger inflammation in organs. Serious immune-related events can include:
- Pneumonitis (lung inflammation), sometimes causing shortness of breath or a new cough
- Hepatitis (liver inflammation), sometimes causing jaundice or right-sided abdominal discomfort
- Colitis (inflammation of the colon), sometimes causing persistent diarrhea or abdominal pain
- Nephritis (kidney inflammation), sometimes causing reduced urine output or lab-detected kidney injury
- Endocrine problems, including thyroid inflammation, adrenal inflammation, or diabetes-related symptoms
- Severe skin reactions and other inflammatory skin conditions
Serious immune reactions often require prompt medical evaluation and may be treated with corticosteroids or other immune-suppressing therapy, depending on severity.
When do Keytruda side effects usually start?
Side effects can appear at different times. Some occur early (during ongoing dosing), while immune-related adverse events can develop later or even after discontinuation. The risk and timing vary by the specific immune-related condition.
Patients are typically monitored with symptom check-ins and blood tests during treatment, which helps catch organ inflammation before it becomes severe.
What side effects should send someone to the ER or call urgently?
Seek urgent medical care if symptoms suggest a severe immune reaction, such as:
- Trouble breathing, new or worsening cough, or chest pain
- Severe or persistent diarrhea, severe abdominal pain, or blood in stool
- Yellowing of the skin/eyes, dark urine, or severe fatigue with signs of liver issues
- Severe weakness, confusion, fainting, or symptoms of dangerously abnormal blood sugar
- Rapidly spreading rash, blistering, or skin peeling
In immune-checkpoint therapies like Keytruda, earlier treatment of severe reactions can reduce complications.
How does Keytruda’s side effect profile compare with other immunotherapies?
Compared with many non-immunotherapy cancer treatments, Keytruda’s standout concern is immune-related toxicity (inflammation of organs and endocrine effects). Other therapies may cause different toxicities (for example, chemotherapy-related nausea, neuropathy, or hair loss), but Keytruda’s key differentiator is immune activation leading to organ-specific inflammation.
If you’re comparing options, the best match depends on your cancer type and medical history, including existing autoimmune disease risk.
Can Keytruda side effects be managed without stopping treatment?
Often, yes. Mild side effects may be managed symptomatically and with close monitoring. More significant immune-related toxicities may lead to holding Keytruda temporarily and starting steroids or other treatments, with a plan that depends on severity and response.
What happens next depends on the specific side effect, lab results, imaging, and how quickly symptoms improve.
Are there special risks for people with autoimmune disease?
Yes. People with autoimmune conditions may have higher risk of immune-related flare-ups or new autoimmune complications because Keytruda activates immune pathways. Treatment decisions usually weigh cancer benefit against the risk of exacerbating underlying autoimmune disease.
Sources
- https://www.drugpatentwatch.com/