Drug Interactions between idelalisib and nirmatrelvir / ritonavir

Idelalisib may cause serious and life-threatening liver problems, and using it with other medications that can also affect the liver such as ritonavir may increase that risk. Ritonavir can also increase the blood levels of idelalisib. In addition to liver problems, this may increase the risk and/or severity of other side effects such as diarrhea, intestinal wall perforation, lung or breathing problems, and low white blood cell and platelet counts. You may need a dose adjustment or more frequent monitoring by your doctor to safely use both medications. Call your doctor immediately if you have fever, chills, joint pain or swelling, unusual bleeding or bruising, skin rash, itching, loss of appetite, fatigue, nausea, vomiting, abdominal pain, dark urine, pale stools, and/or yellowing of the skin or eyes, as these may be signs and symptoms of liver damage. Also let your doctor know if the number of bowel movements per day increases by six or more, or if you experience other potentially serious side effects such as infection, coughing, difficulty breathing, and shortness of breath. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.