Indication
Advanced systemic mastocytosis
Dose
Advanced systemic mastocytosis
- Dose – Oral: 200 mg once daily continuously until disease progression or unacceptable toxicity
Supplied
Available as 25 mg, 50 mg, 100 mg, and 200 mg tablets. Tablets should NOT be crushed or broken. Store at room temperature in original bottle with desiccant and protect from light and moisture.
Pharmacological Category
Tyrosine Kinase Inhibitor that targets KIT and PDGFRA
Administration
Take on empty stomach, 1 hour before or 2 hours after meal
Missed Dose
If a dose is missed, patients should be instructed to take it as soon as they can, unless the next scheduled dose is within 8 hours. If the next scheduled dose is within 8 hours, the patient should skip the missed dose and take the next scheduled.
Adverse Effects
Common: Nausea,Vomiting, Diarrhea, Edema, Thrombocytopenia, Anemia.
Less Common: Photosensitivity, Intracranial hemorrhage, Respiratory tract infection, Confusion, Drowsiness.
The adverse effects listed above are not exhaustive. Please refer to the relevant product monograph for full details.
Monitoring Parameters
Baseline before treatment: Platelet count.
Biweekly for first 8 weeks: platelet count regardless of result.
After first 8 weeks of therapy:
i. If platelet count <75 x 109/L – monitor biweekly;
ii. If platelet count 75-100 x 109/L – monitor monthly;
iii. If platelet count >100 x 109/L – monitor as per physician’s discretion.
Drug Interactions
This drug can impact or be impacted by metabolic enzymes for absorption and excretion. Many drugs can also affect or be affected by these enzymes, so please consult with pharmacy to assess for interactions.
Avoid grapefruit, grapefruit juice, Seville oranges, or Seville orange juice.
Current drug interaction databases should be consulted for more information.
Clinical Pearls
Avoid in pregnancy and lactation.
Limit sun exposure during treatment and 1 week after treatment discontinuation due to photosensitivity. Patients should be counselled on appropriate suncare measures (use of sunscreen, protective clothing, etc.).
References
Blueprint Medicines Corporation. Ayvakyt. Product Monograph. In: Health Canada, Drug Product Database. Available at: https://pdf.hres.ca/dpd_pm/00077104.PDFPublished Sept 18/2024. Accessed February 24th 2025. Lexicomp.
Avapritinib Monograph. In: Lexi-Drugs. Hudson, Ohio: Lexi-Comp, Inc. Accessed February24th, 2025.
