From the Guidelines
Treatment of mast cell activation syndrome (MCAS) should start with H1 antihistamines like cetirizine (10mg daily) or fexofenadine (180mg daily), combined with H2 blockers such as famotidine (20mg twice daily), as these medications have been shown to relieve symptoms caused by secreted histamine 1.
Key Considerations
- The goal of treatment is to reduce the frequency and severity of reactions by targeting multiple pathways of mast cell degranulation and mediator release.
- H1R and H2R antihistamine receptors work better as prophylactic than acute treatment, so it's essential to start treatment early 1.
- Later-generation nonsedating H1R antihistamines, such as fexofenadine and cetirizine, are often used at 2 to 4 times US Food and Drug Administration–approved doses 1.
Additional Treatment Options
- Mast cell stabilizers like oral cromolyn sodium (200mg four times daily before meals) or ketotifen (1-2mg twice daily) may be added to the treatment regimen.
- Leukotriene modifiers such as montelukast (10mg daily) may help with respiratory symptoms.
- Consider low-dose aspirin (81mg daily) if prostaglandin-mediated symptoms are present, but use cautiously as some patients may react negatively.
- For breakthrough symptoms, prescribe epinephrine auto-injectors for severe reactions.
Lifestyle Modifications
- Advise your patient to identify and avoid personal triggers, which commonly include certain foods, medications, temperature extremes, stress, and strong odors.
- A low-histamine diet may benefit some patients.
Severe Cases
- For severe cases unresponsive to first-line treatments, consider omalizumab injections or low-dose corticosteroids for short periods.
- Regular follow-up is essential to adjust medications based on symptom control, as recommended by the AAAAI Mast Cell Disorders Committee Work Group report 1.
From the FDA Drug Label
Cromolyn Sodium Oral Solution (Concentrate) is indicated in the management of patients with mastocytosis. Use of this product has been associated with improvement in diarrhea, flushing, headaches, vomiting, urticaria, abdominal pain, nausea, and itching in some patients. Four randomized, controlled clinical trials were conducted with Cromolyn Sodium Oral Solution (Concentrate) in patients with either cutaneous or systemic mastocytosis;
- Treatment Option: Cromolyn sodium (PO) may be used to treat mast cell activation syndrome, with a dosage of 200 mg QID.
- Clinical Benefits: Improvement in gastrointestinal symptoms, cutaneous manifestations, and cognitive function may be seen in the majority of patients.
- Onset of Action: Clinical improvement may occur within 2-6 weeks of treatment initiation.
- Duration of Action: Clinical benefits may persist for 2-3 weeks after treatment withdrawal. 2 2
From the Research
Treatment Options for Mast Cell Activation Syndrome
- The primary goal of treatment for Mast Cell Activation Syndrome (MCAS) is to control symptoms associated with mast cell mediator release 3.
- Treatment approaches may include:
- Pharmacological options to manage symptoms
- Targeted therapies to block mutant protein variants and/or downstream signaling pathways
- Agents targeting mast cell proliferation, such as kinase inhibitors, in advanced forms of the disease
- H1-antihistamines have been studied as a potential treatment option for primary MCAS, with some evidence suggesting their effectiveness in improving quality of life and symptom control 4.
Pharmacological Treatment
- H1-antihistamines, such as rupatadine, have been shown to improve symptoms in patients with cutaneous and systemic mastocytosis, including itching, wheals and flares, flushing, tachycardia, and headache 4.
- However, the current evidence is limited by the small number of studies and the high risk of bias in these studies 4.
- Further research is needed to fully understand the effectiveness and safety of H1-antihistamines in the treatment of primary MCAS 4.