Trastuzumab Dosing Guide and Precautions

Fam-trastuzumab deruxtecan-nxki (Fam-trastuzumab deruxtecan-nxki) is a drug used to treat breast cancer, non-small cell lung cancer, and gastric cancer. Here are guidelines and precautions for its use:

1. Corresponding gene mutations and tumor specimens need to be tested before use to ensure that the patient is suitable for using trastuzumab. Do not substitute trastuzumab or ado-trastuzumab emtansine.

2. Trastuzumab is an injection preparation. If the patient develops infusion-related symptoms, the infusion rate should be slowed down or interrupted.

3. During intravenous infusion, only infusion sets made of polyolefin or polybutadiene can be used for trastuzumab. The first infusion should take more than 90 minutes. If the previous infusion is well tolerated, the dose may be administered within 30 minutes.

4. Trastuzumab may cause moderate nausea and vomiting, including delayed nausea and/or vomiting. According to local agency guidelines, prophylactic antiemetic medications should be administered to mitigate these adverse effects.

5. For patients with breast cancer and non-small cell lung cancer, the recommended dose of trastuzumab is an intravenous infusion of 5.4 mg/kg every 3 weeks (21-day cycle) until disease progression or unacceptable toxicity. For patients with gastric cancer, the recommended dose is 6.4 mg/kg as an intravenous infusion every 3 weeks (21-day cycle).

6. If adverse reactions occur after using trastuzumab, it may be necessary to temporarily interrupt, reduce the dose, or stop treatment. However, after reducing the dose, do not increase the dose of trastuzumab.

7. If the scheduled dose is delayed or missed, please administer the dose as soon as possible and do not wait until the next scheduled cycle. Adjust the dosing schedule to maintain a 3-week interval between doses and determine the dose and rate based on the patient's tolerance of the most recent infusion.

8. If severe infusion reaction occurs, please permanently discontinue trastuzumab.

9. For patients with breast cancer and non-small cell lung cancer, if severe infusion reactions occur, the first dose of trastuzumab should be reduced to 4.4 mg/kg, and the second dose of trastuzumab should be reduced to 3.2 mg/kg. If further reduction is still needed, treatment should be stopped. For patients with gastric cancer, the first dose is reduced to 5.4 mg/kg and the second dose is reduced to 4.4 mg/kg. If further reduction is still required, treatment is stopped.