Drug Interaction Report

Vandetanib may increase the blood levels of larotrectinib in some patients. This may increase the risk and/or severity of side effects such as dizziness, confusion, coordination problems, memory problems, liver problems, and tingling, numbness or burning in the hands and feet. Talk to your doctor if you have any questions or concerns. Your doctor may be able to prescribe alternatives that do not interact, or you may need a dose adjustment or more frequent monitoring to safely use both medications. You should seek immediate medical attention 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. 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 can increase the blood levels of larotrectinib. This may increase the risk and/or severity of side effects such as dizziness, confusion, coordination problems, memory problems, liver problems, and tingling, numbness or burning in the hands and feet. You should avoid the consumption of grapefruit and grapefruit juice during treatment with larotrectinib. Talk to your doctor or pharmacist if you have questions on this or other medications you are prescribed. 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.

The recommended maximum number of medicines in the 'multikinase inhibitors' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'multikinase inhibitors' category:

• vandetanib
• Vitrakvi (larotrectinib)

Note: In certain circumstances, the benefits of taking this combination of drugs may outweigh any risks. Always consult your healthcare provider before making changes to your medications or dosage.