Alpatin® Eye Drop is the preparation of Epinastine 0.05%. 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 α1-, α 2-, and 5-HT2–receptors. Some anti-allergic agents markedly inhibit basal tear production due to the blockade of muscarinic-3 receptor. Epinastine causes minimal inhibition of muscarinic-3 receptors leading to limited interference in the tear secretion.