Pemirolast (INN) is a mast cell stabilizer used as an anti-allergic drug therapy. It is marketed under the tradenames Alegysal and Alamast. The compound acts by inhibiting antigen-induced mast cell degranulation, reducing release of histamine and other inflammatory mediators, and is primarily formulated as an ophthalmic potassium salt solution for allergic conjunctivitis (typical ophthalmic concentration 0.1% w/v). Clinically it is used topically to reduce ocular itching and redness associated with allergic conjunctivitis. From a pharmaceutical standpoint, pemirolast is supplied as a white to off-white crystalline powder with low aqueous solubility in the free acid form, improved solubility as the potassium salt, and requires sterile aqueous formulation for ophthalmic administration. Standard manufacturing controls address residual solvents, specified related substances, and sterility/endotoxin limits for topical ophthalmic products, and the molecule demonstrates acceptable stability under controlled conditions when protected from extreme pH and prolonged light exposure.
Parent: Pemirolast
Typical quality control limits for pemirolast active pharmaceutical ingredient follow ICH Q3A style criteria and industry practice: individual unspecified related substances not greater than 0.1% w/w, total unspecified impurities not greater than 0.5% w/w. Specified process or degradation related compounds commonly addressed in specifications include a dealkylation impurity, a hydrolysis product and a low level oxidation product, each typically limited to 0.1 to 0.2% w/w depending on the impurity qualification status. Residual solvent limits follow ICH Q3C, with class 2 solvents used in manufacture limited to approximately 0.5% w/w or lower, and residual water controlled by water content testing. Heavy metals are controlled to pharmacopeial limits, commonly not more than 10 to 20 ppm, and sterile ophthalmic formulations specify microbial limits and bacterial endotoxin limits consistent with ophthalmic product requirements, for example endotoxin below 0.5 EU/mL. Final specification values are set by the marketing authorization dossier and pharmacopeial monograph applicable to the product.
Pemirolast is an anti-allergic medication classified as a mast cell stabilizer that prevents antigen-triggered mast cell degranulation, reducing release of histamine and other mediators; it is most commonly used as an ophthalmic solution for allergic conjunctivitis and is marketed under names such as Alegysal and Alamast.
Reported adverse effects for topical pemirolast formulations, including products marketed as pemirox, are primarily local and transient: ocular burning or stinging on instillation, eye irritation, hyperemia, itching, and foreign body sensation; uncommon systemic effects include headache or altered taste; rare hypersensitivity or allergic reactions have been reported and any new or severe symptoms should prompt medical review.
Pemirolast is generally considered to have low systemic exposure when used as a topical ophthalmic agent and is categorized in many regulatory references as pregnancy category B based on available animal data showing no evidence of teratogenicity and limited human data; use in pregnancy should follow a benefit risk assessment by the treating clinician.
Alamast, an ophthalmic formulation of pemirolast, commonly causes mild, transient local effects such as burning or stinging at the application site, eye irritation, watering or redness, and occasionally an unpleasant taste; serious adverse events are rare, but patients with signs of hypersensitivity should stop use and seek medical advice.
