Avapritinib is a kinase inhibitor primarily used for the treatment of unresectable or metastatic gastrointestinal stromal tumors carrying PDGFRA exon 18 mutations. The dosage needs to be adjusted based on the patient's weight and liver function. Special attention should be paid to pregnancy, lactation, and liver and kidney dysfunction in special populations.

1. Usage and Dosage

(1) Recommended dosage for adults: Take 300mg orally once daily, and continue treatment until disease progression or unacceptable toxicity occurs.

(2) Dose adjustment: In case of Grade 3 or higher adverse reactions, reduce the dosage to 200mg/day for the first reduction, and then reduce it to 100mg/day for the second reduction.

(3) Administration method: Swallow the entire tablet, which can be taken with food or on an empty stomach. Avoid combining it with strong CYP3A inhibitors.

2. Medication for special populations

(1) Pregnancy: Based on animal studies, there may be harm to the fetus. The pregnancy status needs to be verified before treatment, and the risks need to be informed during pregnancy.

(2) Lactation: It is not clear whether the drug enters human milk. It is recommended to avoid breastfeeding during treatment and for 1 week after drug withdrawal.

(3) Liver function impairment: No adjustment is needed for mild impairment (Child-Pugh Class A), a 50% reduction is required for moderate impairment, and it is prohibited for severe impairment.

(4) Renal dysfunction: No dosage adjustment is required for mild to moderate impairment. However, there is no experience with use in patients with severe impairment or undergoing dialysis.

(5) Pediatric patients: Safety and efficacy have not been established, and use is not recommended for patients under 18 years of age.

(6) Elderly patients: Patients aged 65 and above require close monitoring for adverse reactions, but routine dosage adjustments are not necessary.

3. Medication precautions

(1) Cognitive effects: May cause attention disorders and memory impairment. Avoid driving or operating machinery during medication.

(2) Bleeding risk: Monitor for bleeding symptoms during treatment, and discontinue the medication in patients with severe thrombocytopenia.

(3) Liver function monitoring: Regularly check liver function before and during treatment, and promptly address any abnormalities that arise.