Tranilast

Mast-cell mediator-release inhibitor · also known as Rizaben, N-5'

Oral anti-allergic medicine approved in Japan; direct mast-cell experiments measure mediator release and exocytosis in rat cells.

How it relates to mast cells: Mast cells in the laboratory
Types of studies cited: Non-human mast cells in vitro , Animal model
Approved outside the US for: bronchial asthma, allergic rhinitis, atopic dermatitis, keloids and hypertrophic scars

What this relationship means: Studied on mast cells directly, but in cell culture or animals rather than in people. The study-design field distinguishes human cells from non-human models. A mechanism demonstrated in a dish is a reason to investigate, not a result — and the concentrations used are frequently ones that human exposure does not reach.

Mechanism of action

Tranilast is an oral anti-allergic medicine whose Japanese label describes inhibition of histamine, leukotriene, and other mediator release from mast cells and other inflammatory cells. Laboratory studies have examined antigen-triggered histamine release, calcium uptake, membrane deformation, and exocytosis in rat peritoneal mast cells.

Those experiments support calling tranilast a laboratory-studied mast-cell stabilizer, but they do not supply a human MCAS result. A double-blind controlled comparison in perennial allergic rhinitis included tranilast, cromolyn, and placebo groups; the PubMed record does not identify the allocation as randomized, so this page does not display a randomized-trial badge for that study.

Regulatory context is formulation- and country-specific. Rizaben capsules, fine granules, and dry syrup appear in the current Japanese PMDA prescribing information. The non-US approval tag records that fact separately from the mast-cell relationship and from any question of MCAS use.

Approved elsewhere — off-label rationale

Japan's current PMDA-listed Rizaben label identifies tranilast as a prescription medicine for bronchial asthma, allergic rhinitis, atopic dermatitis, and keloids or hypertrophic scars. It is included here because published experiments directly test mast-cell mediator release and exocytosis, not because a Japanese approval establishes an MCAS indication.

Sources

A clinical evaluation of N-5' with perennial-type allergic rhinitis—a multi-clinic, intergroup, double-blind comparative test Peer-reviewed study 1984 PMID 6205614 · link checked 21 Aug 2026
Study of the mechanism of inhibitory action of tranilast on chemical mediator release Peer-reviewed study 1988 PMID 2452912 · link checked 21 Aug 2026
Anti-Allergic Drugs Tranilast and Ketotifen Dose-Dependently Exert Mast Cell-Stabilizing Properties Peer-reviewed study 2016 PMID 26741745 · link checked 21 Aug 2026
Rizaben (tranilast) Japanese prescribing information Drug label · link checked 21 Aug 2026

What this evidence cannot establish

The direct mast-cell experiments used rat peritoneal mast cells or animal models, and some exocytosis changes were reported only at relatively high in-vitro concentrations. The controlled human comparison enrolled people with perennial allergic rhinitis rather than MCAS and did not establish a human MCAS mechanism or outcome. The current Japanese label contraindicates use during pregnancy and lists cystitis-like symptoms, hepatic or renal dysfunction, and blood-count abnormalities among serious adverse reactions.

What this page does not say

No dosing, and no claim that this works. The entry describes a published mechanism, the cited study types, and what those studies cannot establish — nothing further. Why the site is built this way.

Recently verified. Verified 21 Aug 2026