2015留抗过敏.pptVIP

Histamine and Antihistamines;[Histamine Pharmacology] 1. First autacoid to be discovered. 2. Synthesized in 1907 3. Demonstrated to be a natural constituent of mammalian tissues (1927) 4. Involved in inflammatory and anaphylactic reactions. 5. Local application causes swelling redness, and edema, mimicking a mild inflammatory reaction. 6. Large systemic doses leads to profound vascular changes similar to those seen after shock or anaphylactic origin;Storage and release of Histamine: 1. Most histamine:in granules in?mast cells?and in white blood cells called?basophils?and?eosinophils. 2. Mast cells: at sites of potential injury-the nose, mouth, and feet, internal body surfaces, and blood vessels. 3. Non-mast cell histamine is found in several tissues, including the?brain, where it functions as a neurotransmitter. 4. Another important site : stomach. ;;;Pharmacological Effects of Histamine 1. Cardiovascular system. (1) reddening at injection site due to vasodilation (2) wheal or disk of edema (3) a bright crimson flare surrounding the wheal (4) i.v. histamine: lowered blood pressure, flushing, rise in skin temperature, intense headache. 2. Smooth muscle of bronchioles: contraction 3. Exocrine glands: enhanced secretion 4. Peripheral Nervous system: itching and pain;Pharmacological Effects: Exocrine Glands Gastric glands Salivary glands Sweat glands Pancreas Bronchial glands Lacrimal glands;Pharmacological Effects: Arterioles, Capillaries Venules 1. Vasodilation 2. Increased permeability, (edema) 3. Systemic hypotension;General Mechanism of Action of Antihistamines 1. Blocks action of histamine at receptor 2. Competes with histamine for binding 3. Displaces histamine from receptor 4. Most beneficial when given early;Therapeutic Uses of H1 Blockers 1. Allergic rhinitis, 2. Common cold 3. Allergic dermatoses 4. Outpatient procedures for preanesthetic sedation and prevention of nausea and vomiting 5. Antiemetic 6. Hypnotics 7. Other uses: Redu