Read the Medication Guide provided by your pharmacist before you start using trastuzumab deruxtecan and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

This medication is given by slow injection into a vein by a health care professional. It is given as directed by your doctor, usually once every 3 weeks. Your first infusion will be given over at least 90 minutes.

The dosage, the speed of your injection, and the length of time you receive trastuzumab deruxtecan are based on your body weight, medical condition, and response to treatment.

To get the most benefit from this medication, do not miss any doses. To help you remember, mark your calendar with a reminder.