Keytruda: Uses, How It Works, and Common Side Effects

Keytruda is a prescription medication used to treat certain cancers, including lung cancer, breast cancer, Hodgkin lymphoma, and many more.

It is a type of immunotherapy that helps the immune system detect and fight cancer cells.

Depending on the stage and type of cancer, it can be used alone or with chemotherapy, radiotherapy, or surgery.

Keytruda works by blocking a protein called PD-1 on the surface of certain immune cells called T cells.

Once PD-1 is blocked, the T cells are more able to find and kill cancer cells.

This medicine is given as a slow infusion into a vein over 30 minutes and is usually given every 3 to 6 weeks.

The most common side effects when used alone are tiredness, muscle and joint pain, rash, diarrhea, fever, cough, reduced appetite, itchy skin, difficulty breathing, constipation, pain, abdominal pain, nausea, and hypothyroidism.

These side effects can occur in 20% or more of patients.

This is not a complete list of side effects, and others may occur.

This material is provided for educational purposes only and is not intended for medical advice, diagnosis, or treatment.

Always consult with your healthcare provider.

References:
1. Drugs.com. Updated Aug 2025. Keytruda: Package Insert / Prescribing Info. Retrieved from https://www.drugs.com/pro/keytruda.html
2. Keytruda [package insert]. Updated Aug 2025. Merck Sharp & Dohme LLC. Retrieved from: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=9333c79b-d487-4538-a9f0-71b91a02b287