H-1 antihistamines.ppt

Anti-Allergy Drugs Allergies 50 million people in the US suffer from allergies 20% of the population 3.5 million lost work days per year 2 million lost school days per year Anti-Allergy Drugs Allergies Causes Treatment Antihistamines First Generation Second Generation Decongestants Anti-inflammatories What is an Allergy? Body responds adversely to normally harmless external substances called allergens What Causes Allergies? Allergic response is mediated by antibodies Proteins produced by body’s immune system to help remove foreign substances Bind with a distinct three dimensional molecular shape substances Proteins Complex Sugars What Causes Allergies? IgE antibodies mainly responsible for allergic reactions Binds with receptors in cell membranes of mast cells and basophils in blood Binding of IgE antibodies to mast cells causes release of histamine Histamine ?-Imidazole-ethylamine Synthesized in mammalian tissues by decarboxylation of L-histidine Histamine What Causes Allergies? What Causes Allergies? Histamine binds to H1 receptors bronchi of lungs blood vessels pain/itch nerve endings in skin What Causes Allergies? Histamine causes dilation of blood vessels Blood pressure drops Vessels become more permeable Fluid is able to escape into the surrounding tissue causing swelling Histamine stimulates sensory nerve endings Sneezing, itching Histamine can cause bronchial spasms How are allergies treated? Antihistamines Decongestants Anti-inflammatories Antihistamines Daniel Bovet, Nobel Prize 1944 Synethesized first antihistaminic compounds Appear to prevent the binding of histamines to H1 receptors through their structural similarities Antihistamines Antihistamines First Generation Six classes Alkylamines Ethanolamines Ethylenediamines Piperazines Phenothiazines Piperadines First Generation Antihistimines(Alkylamines) Chlorpheniramine maleate (Chlor Trimeton?) Schering (1949) Currently sold OTC First Generation Antihistimines (Ethanolamines) Diphenhydram