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Histamine is widely, if unevenly, distributed throughout the animal kingdom and is present in many venoms, bacteria, and plants
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tarix | 26.05.2018 | ölçüsü | 461 b. | | #46164 |
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Histamine is widely, if unevenly, distributed throughout the animal kingdom and is present in many venoms, bacteria, and plants. Histamine is widely, if unevenly, distributed throughout the animal kingdom and is present in many venoms, bacteria, and plants.
Immunologic release Immunologic release - histamine plays a central role in immediate hypersensitivity and allergic responses
- The release of histamine only partially explains the biological effects that ensue from immediate hypersensitivity reactions
Chemical and mechanical release - Tubocurarine, succinylcholine, morphine
Mechanism of action Mechanism of action Tissue and organ system effect - Nervous system
- Cardiovascular system
- Bronchial smooth muscle
- Gastrointestinal tract smooth muscle
- Other smooth muscle organs
- Secretary tissue
- Metabolic effects
- The triple response
- Other effects possibly mediated by histamine
regulation of drinking regulation of drinking body temperature control of blood pressure perception of pain wakefulness
Vasodilation Vasodilation Increased "Capillary" Permeability Triple Response of Lewis Heart Histamine Shock
Contraction is due to activation of H1 receptors Contraction is due to activation of H1 receptors relaxation (for the most part) is due to activation of H2 receptors
regulator of gastric acid secretion
Pain
Clinical use Clinical use - a diagnostic agent
- to assess nonspecific bronchial hyperreactivity in asthmatics
- as a positive control injection during allergy skin testing
Toxicity and contraindications
H1 receptor antagonists H1 receptor antagonists H2 receptor antagonists
Absorption, distribution Absorption, distribution Metabolism: - Astemizole and Terfenadine
Smooth Muscle Smooth Muscle Capillary Permeability Flare and Itch Central Nervous System - Can both stimulate and depress the CNS
Histamine receptor blockade Histamine receptor blockade Other actions - Sedation
- Antinausea and antiemetic actions
- Antiparkinsonism effects
- Antichlinoceptor effect: Promethazine
- Adrenoceptor blocking action
- Serotonin blocking action
- Local anesthesia: Promethazine
Clinical use Clinical use - Allergic reaction
- Motion sickness and vestibular disturbance
- Nausea and vomiting of pregnancy?
Toxicity - Sedation, antimuscarninc action,
- Drug allergy
- Drug interaction
- Teratogenic effects
Despite persistent popular belief, H1 antagonists are without value in combating the common cold. Despite persistent popular belief, H1 antagonists are without value in combating the common cold.
Mechanism of action
Serotonin agonists Serotonin agonists Serotonin antagonists
Phenoxybenzamine (5HT2) - Phenoxybenzamine (5HT2)
- Cyproheptadine (5HT2)
- Ketanserin (5HT1C)
- Odansetrone (5HT3)
Sertonin related to sleep, emotion, sex, and appetite Sertonin related to sleep, emotion, sex, and appetite Could reduce food intake - Fenfluramine, dexfenfluramine
- Cause serotonin release and inhibition of food uptake
Toxicity: - fatal and nonfatal pulmonary hypertension
- Valvular lesions
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