Cromolyn sodium is a mast cell stabilizer that prevents mast cell degranulation — the release of histamine, prostaglandins, leukotrienes, and other inflammatory mediators that drive symptoms in mast cell activation syndrome (MCAS), mastocytosis, and allergic GI conditions.

Unlike antihistamines that block histamine receptors after release, cromolyn prevents the release itself — acting upstream of the histamine response. This makes it a true preventative treatment rather than symptomatic relief.

Oral cromolyn is poorly absorbed and acts almost entirely within the GI lumen, making it exceptionally safe with minimal systemic effects. Compounded oral cromolyn sodium provides the same active ingredient as the FDA-approved Gastrocrom at dramatically lower cost — critical for MCAS patients who need long-term, consistent treatment.

Mast Cell Membrane Stabilization
Cromolyn sodium inhibits IgE-mediated and non-IgE-mediated mast cell degranulation by blocking calcium ion influx across the mast cell membrane — preventing the intracellular signaling cascade that triggers mediator release.

Local GI Action
Oral cromolyn is minimally absorbed (<1% systemic bioavailability), acting directly on mast cells throughout the GI mucosa. This produces targeted GI mast cell stabilization without significant systemic effects.

Standard MCAS dosing: 100–200mg (1–2 ampules of Gastrocrom equivalent) 4x daily, 30 minutes before meals and at bedtime

Maintenance: Lowest effective dose — some patients do well on 2x daily

Cromolyn must be taken consistently and preventatively — it does not provide acute relief. Allow 2–4 weeks at therapeutic dose to assess efficacy.

Start at 100mg twice daily and increase to 4x daily dosing over 1–2 weeks as tolerated. Cromolyn is preventative — it must be taken before mast cell triggers (especially meals) to be effective. Some patients notice GI symptoms temporarily worsen in the first week before improving.