The active ingredient of keytruda is pembrolizumab which belongs to the Drug class PD-1 (Programmed cell death protein) inhibitors. Dosage and duration of the medication is decided by the doctor. Keytruda is used for classical Hodgkins lymphoma, non-small cell lung cancer(NSCLC), cervical cancer and other advanced cancers. Some common side effects may be seen in patients such as fever, constipation, weight loss, loss of appetite, muscle and joint pain.