indication

For the prevention of itching of the eyes caused by allergies such as hay fever, and allergic conjunctivitis

pharmacology

Pemirolast is used for the prophylactic treatment of itching of the eye associated with allergic conjunctivitis. Pemirolast potassium is a mast cell stabilizer that inhibits the in vivo Type I immediate hypersensitivity reaction. Pemirolast inhibits the antigen-induced release of inflammatory mediators (e.g., histamine, leukotriene C4, D4, E4) from human mast cells. Allergic reactions lead to cell-degranulation and the release of histamine (and other chemical mediators) from the mast cell or basophil. Once released, histamine can react with local or widespread tissues through histamine receptors. Histamine, acting on H₁-receptors, produces pruritis and vasodilatation (allowing blood fluids to enter the area to cause swelling). Pemirolast is a histamine H1 antagonist. It competes with histamine for the normal H₁-receptor sites on effector cells of blood vessels to provide effective, temporary relief of watery and itchy eyes.

mechanism of action

Pemirolast binds to the histamine H₁ receptor. This blocks the action of endogenous histamine, which subsequently leads to temporary relief of the negative symptoms brought on by histamine. Pemirolast has also been observed to inhibit antigen-stimulated calcium ion influx into mast cells through the blockage of calcium channels. Pemirolast inhibits the chemotaxis of eosinophils into ocular tissue, and prevents inflammatory mediator release from human eosinophils.

biotransformation

Hepatic (Ophthalmic)

half life

4.5 hours (Ophthalmic)

route of elimination

Following topical administration, about 10-15% of the dose was excreted unchanged in the urine.