Antihistamines week 5 Flashcards
What are the effects of hypersecretion of serotonin? What is the usual source?
- Malignant growth of enterochromaffin cells (usually in small intestines)
- increase in synthesis and release of 5HT
– Also increse substance P, prostaglandins, bradykinin
• Release results in intestinal hypermotility, diarrhea, bronchial constriction, hypotension, cardiac fibrosis
What are the primary receptors of the chemoreceptor trigger zone in the area postrema?
Primary receptors are D2 dopamine receptors and 5HT3 serotonin receptors
Metoclopramide (Reglan)
D2 receptor antagonist. anti-emetic
Prochloperazine (Compazine)
D2 receptor bloocker. antiemetic
Ritanserin
antagonizes 5HT2 receptor present in cerebral cortex, platelets, and smooth muscle. Signals via IP3 and DAG
antiplatelet
Chlorpromazine (Thorazine)
D2 receptor blocker. anti emetic
Meclizine
antihistamine, anti muscaraninc, anti emetic used for motion sickness
Cyproheptadine
antagonizes 5HT2 receptor present in cerebral cortex, platelets, and smooth muscle. Signals via IP3 and DAG
Controlling skin allergies, itching, cold induced urticaria, and for smooth muscle actions of serotonin in carcinoid tumor and gastrectomy
Ondansetron
antagonizes 5HT3 receptor present in CTZ (chemoreceptor trigger zone in area postrema)
Prophylactic for nausea vomiting in cancer chemotherapy
Methysergide
antagonizes 5HT2 receptor present in cerebral cortex, platelets, and smooth muscle. Signals via IP3 and DAG
A partial agonist/antagonist 5HT2 receptors -prophylactic use for migraines
Promethazine (Phenergan)
weak D2, strong antihistamine, and strong anticholinergic effects. Anti motion, strong sedation
*weak D2 binding suggest that it would be a poor choice for opiod related nausea. Remeber that opiods can directly activate the CTZ which contains mostly D2 and 5HT3 receptors.
