indication

For the prevention of itching associated with allergic conjunctivitis.

pharmacology

Epinastine is an antihistamine and an inhibitor of histamine release from the mast cell for topical administration to the eyes. Epinastine is indicated for the prevention of itching associated with allergic conjunctivitis. Epinastine is a topically active, direct H₁-receptor antagonist and an inhibitor of the release of histamine from the mast cell. Epinastine is selective for the histamine H₁-receptor and has affinity for the histamine H2 receptor. Epinastine also possesses affinity for the a1-, a2-, and 5-HT₂ -receptors. Epinastine does not penetrate the blood/brain barrier and, therefore, is not expected to induce side effects of the central nervous system.

mechanism of action

Epinastine has a multiaction effect that inhibits the allergic response in 3 ways: 1. stabilizes mast cells by preventing mast cell degranulation to control the allergic response, 2. prevents histamine binding to both the H1- and H₂-receptors to stop itching and provide lasting protection, and 3. prevents the release of proinflammatory chemical mediators from the blood vessel to halt progression of the allergic response.

biotransformation

Mainly excreted unchanged, less than 10% metabolized.

absorption

The absolute bioavailability of epinastine is about 40%.

half life

12 hours

route of elimination

Epinastine is mainly excreted unchanged. The renal elimination is mainly via active tubular secretion.