Chloropyramine

Chloropyramine is a first-generation antihistamine drug approved in several Eastern European countries such as Russia for the treatment of allergic conjunctivitis, allergic rhinitis, bronchial asthma, and other atopic (allergic) conditions. Related indications for clinical use include angioedema, allergic reactions to insect bites, food and drug allergies, and anaphylactic shock. Chloropyramine 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 chloropyramine can be used by researchers for the purposes of blocking the effects of histamine on cells and tissues. In addition, chloropyramine has some anticholinergic properties. Chloropyramine's anticholinergic properties and the fact that it can pass through the blood–brain barrier are linked to its clinical side effects such as drowsiness, weakness, vertigo, fatigue, dry mouth, constipation, and rarely — visual disturbances and increase of intraocular pressure.