Autocoids Flashcards
Histamine
Formed by decarboxylation of AA L-histidine
Immunologic release
Chemical and mechanical release
Drugs: morphone and tubocurarine
Found: lungs, skin, and GI
Released by mast cells and by type I hypersensitivity rxns with GPCRS
Histamine receptors (4)
H1: Smooth muscle, endothelium, brain
H2: Gastric mucosa, cardiac muscle, mast cells
H3: Presynaptic autoreceptors
H4: Eosinophils, neutrophils
H1 Activation
Hypotension: via NO (vasodilation)
Edema: Increase capillary permeability
Bronchospasm, increase pain and pruritis
H1 receptors Antagonists: Indications
Allergic reactions
Nausea and vomiting
Sleep aids and cold meds
H1 receptors Antagonists: Adverse Effects
Anticholinergics due to muscarinic blockade
Sedation
Except Loratadine, Cetirizine, Fexofenadine
H1 receptors Antagonists Buzzword and Drugs
Sedation Diphenhydramine (OTC) Promethazine (slight alpha blockade) Cholorpheniramine Meclizine (for motion sickness) Hydroxyzine
No drowsiness nor sedation, doesn’t cross BBB
Loratadine, Cetirizine, Fexofenadine
H2 Activation
Increase HCL secretion
Increase SA Nodal rate, increase contractility
H2 Receptor Antagonists MOA
Block HCL secretion
Block secretory responses to food
H2 Receptor Antagonists
Cimetidine
Famotidine
Ranitidine
Rx of indigestion, heart burn, duodenal ulcer, Zollinger-Ellison syndrome
H2 Receptor Antagonists Adverse Effects:
1 - Cimetidine inhibits Cyp450 —> decrease metabolism of drugs and increased toxicity
theophylline, warfarin, phenytoin, diazepam
2 - Cimetidine decreases androgens: gynecomastia and decrease libido
3 - Famotidine: Blood dyscrasias (blood abnormality similar to thrombocytopenia, leukopenia, and agranulo cytosis
4 - Smoking decreases effects of H2 blockers
Scopolamine
Anti-cholinergic indicated to prevent nausea and vomting, by blocking the Labyrinthine Vestibular system
Buzz word: Motion sicknexx
Side effects: dry mouth, urinary retention, constipation
Serotonin (5HT) Receptor Drugs: Buspirone
5HT1A,
Rx of GAD
Serotonin (5HT) Receptor Drugs: Sumatriptan
5HT1D
Migraine
Serotonin (5HT) Receptor Drugs: Olanzapine
5HT2A
Antipsych
Serotonin (5HT) Receptor Drugs: Cyprohepatadine
5HT2
H1-Blocker
Serotonin (5HT) Receptor Drugs: *Ondansetron
5HT3
Antiemetic
*antagonist
Serotonin (5HT) Receptor Drugs: Tegaserod
5HT4
IBD constipation
Ergot Alkaloids: Ergotamine
Mixed partial agonist at 5 HT2 and alpha adrenoreceptor
Rx: Migraine and cluster headache
Ergot Alkaloids: Ergonovine
mixed partial agonist at 5 HT2 and alpha adrenorecptor
Rx: Post partum bleeding and migraine headache
Ergot Alkaloids: LSD
CNS 5 HT2 and dopamine agonist
5 HT2 antagonist in periphery
Not Used but widely abused
Ondansetron
5HT3 Receptor antagonists (all “setrons:
Anti-emetic at CTZ (area postrema) and GI tract
Buzzword: nausea and vomiting due to cancer drugs
Ondansetron: Adverse Effects:
Headache may occur with ondansetron
abdrominal cramps, dry mouth
New Drug: Tegaserod
5-HT4 AGONIST
New Drug: Tegaserod MOA
Activation of the 5HT4 receptors –> stimulates the peristaltic reflex
New Drug: Tegaserod Buzzword
Irritable Bowel Syndrome for constipation in women
