<unk>  is a classical ("old" or first generation) antihistamine drug approved in some Eastern European countries for the treatment of allergic conjuctivitis, allergic rhinitis, bronchial asthma, and other atopic (allergic) conditions. Related indications for clinical use include Quincke's edema, allergic reactions to insect bites, food and drug allergies, and anaphylactic shock.<unk>  is known as a competitive reversible H1-receptor antagonist (also known as an H1 inverse agonist), meaning that it exerts its pharmacological action by competing with histamine for the H1 subtype histamine receptor. By blocking the effects of histamine, the drug inhibits the vasodilation, increased vascular permeability, and tissue edema associated with histamine release in the tissue. The H1-antagonistic properties of<unk>  can be used by researchers for the purposes of blocking the effects of histamine on cells and tissues. In addition,<unk>  has some anticholinergic properties.<unk> 's anticholinergic properties and the fact that it can pass through the blood-brain barrier are linked to its clinical side effects: drowsiness, weakness, vertigo, fatigue, dryness in the mouth, constipation, and rarely - visual disturbances and increase of intraocular pressure.
Chloropyramine
Meclizine
Terfenadine
Cetirizine hydrochloride
Tyramine
Diphenhydramine 
Diphenylpyraline
Methyl salicylate