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 control skin, gastrointestinal, and neurologic symptoms 1. The goal of treatment is to relieve symptoms caused by secreted histamine and to stabilize mast cells.
- H1R and H2R antihistamine receptors work better as prophylactic than acute treatment because once signs or symptoms of histamine-mediated effects are apparent, it is too late to block the binding of that histamine to its receptors.
- Mast cell stabilizers like oral cromolyn sodium (200mg four times daily before meals) or ketotifen (1-2mg twice daily) can be added to the treatment regimen to reduce abdominal bloating, diarrhea, and cramps, and may also help with neuropsychiatric manifestations 1.
- For patients with gastrointestinal symptoms, consider adding a proton pump inhibitor like omeprazole (20-40mg daily) to the treatment regimen.
- Leukotriene modifiers such as montelukast (10mg daily) may help with respiratory symptoms, particularly if urinary LTE4 levels are increased 1.
- For breakthrough symptoms, provide an epinephrine auto-injector for severe reactions, and advise patients to identify and avoid triggers including certain foods, medications, temperature extremes, and stress.
- Consider low-dose aspirin (81mg daily) if prostaglandin-mediated symptoms are present, but use cautiously as it may trigger reactions in some patients 1.
- Corticosteroids should be reserved for severe flares, as they may have significant side effects, particularly with long-term use 1. This approach targets multiple mediator pathways involved in mast cell activation, addressing the underlying pathophysiology of excessive mast cell degranulation and mediator release that causes the diverse symptoms in MCAS.
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; To treat mast cell activation in your patient, consider using Cromolyn Sodium Oral Solution (Concentrate), as it has been associated with improvement in symptoms such as:
- Diarrhea
- Flushing
- Headaches
- Vomiting
- Urticaria
- Abdominal pain
- Nausea
- Itching The recommended dosage is 200 mg QID 2. Clinical improvement can be expected to occur within 2-6 weeks of treatment initiation and may persist for 2-3 weeks after treatment withdrawal 2.
From the Research
Treatment Options for Mast Cell Activation
- Patients with mast cell activation syndrome (MCAS) may present with symptoms of mast cell activation, and treatment options include blockade of mediator receptors, inhibition of mediator synthesis, and anti-IgE therapy 3.
- H1-antihistamines have been shown to be effective in treating primary MCAS, with significant improvements in quality of life, symptom control, and reduction in itching and whealing 4.
- Quercetin has been found to be more effective than cromolyn in blocking human mast cell cytokine release and inhibiting contact dermatitis and photosensitivity in humans 5.
Medications for Mast Cell Activation
- H1-antihistamines, such as rupatadine, have been shown to be effective in treating MCAS, with significant improvements in symptom control and quality of life 4.
- Cromolyn has been used as a mast cell stabilizer, but its effectiveness and selectivity have been questioned, particularly in mice 6.
- Cromolyn sodium has been found to differentially regulate human mast cell and mouse leukocyte responses to control allergic inflammation, with immunomodulatory actions that are broader than only mast cell stabilization 7.
Management of Acute Episodes
- Acute episodes of mast cell activation require epinephrine, and prolonged episodes may be addressed with corticosteroids 3.
- Patients with clonal mast cell syndromes may need a reduction in the number of mast cells to prevent severe symptoms, including anaphylaxis and/or progression to aggressive diseases 3.