Drug Interaction Report

Selpercatinib may increase the blood levels of repaglinide. You may be more likely to experience side effects such as hypoglycemia, or low blood sugar, that can sometimes occur with the use of repaglinide. Symptoms of hypoglycemia include headache, dizziness, drowsiness, nervousness, weakness, tremor, nausea, hunger, sweating, and palpitation. The risk of other serious but uncommon side effects such as fluid retention, macular edema (swelling in the back of the eye), new or worsening heart failure, bone fractures, anemia, and liver problems may also be increased. You may need a dose adjustment or more frequent monitoring of your blood sugar and other tests to safely use both medications. Contact your doctor immediately if you experience blurred vision or other visual abnormalities; excessive or rapid weight gain; swelling in the ankles or legs; shortness of breath or difficulty breathing; unusual tiredness; chest pain or tightness; or worsening of existing heart problems. You should also seek prompt medical attention if you develop signs and symptoms of liver damage such as fever, chills, joint pain or swelling, unusual bleeding or bruising, skin rash, itching, loss of appetite, fatigue, nausea, vomiting, dark colored urine, light colored stools, and yellowing of the skin or eyes. 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.

You should limit or avoid consumption of grapefruit and grapefruit juice during treatment with selpercatinib unless directed otherwise by your doctor. Grapefruit juice may increase the blood levels of selpercatinib. High levels of selpercatinib can increase the risk of an irregular heart rhythm that may be serious and potentially life-threatening, although it is a relatively rare side effect. You may be more susceptible if you have a heart condition called congenital long QT syndrome, other cardiac diseases, conduction abnormalities, or electrolyte disturbances (for example, magnesium or potassium loss due to severe or prolonged diarrhea or vomiting). The risk and/or severity of other side effects may also increase, including nausea, vomiting, constipation, diarrhea, rash, muscle and joint pain, swelling of arms or legs, liver problems, high blood pressure, and bleeding complications. Talk to your doctor if you experience intolerable or troublesome side effects, or you have other questions or concerns. You should seek immediate medical attention if you develop sudden dizziness, lightheadedness, fainting, shortness of breath, or heart palpitations during treatment with selpercatinib. 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.

Grapefruit juice may increase the blood levels of certain medications such as repaglinide. You may want to limit your consumption of grapefruit and grapefruit juice during treatment with repaglinide. However, if you have been regularly consuming grapefruit or grapefruit juice with the medication, then it is advisable for you to talk with your doctor before changing the amounts of these products in your diet, as this may alter the effects of your medication. Contact your doctor if your condition changes or you experience increased side effects. Orange juice is not expected to interact.