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58 Cards in this Set
- Front
- Back
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Where is histamine stored?
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tissues - mast cells
blood - basophils, platelets epidermis, CNS, regenerating cells - found in non-mast cells as well |
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What causes histamine release
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-type I (IgE-mediated) hypersensitivity reactions, tissue injury, drugs, compounds
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What are the major symptoms of IgE-sensitized histamine release
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-bronchoconstriction, decreased Pa, increased capillary permeability, edema
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All histamine receptors are what kind of receptor
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GPCR
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H1 receptors:
stimulate causes |
-PLC - increased Ca which produces contraction in muscle and EDRF release causing vasodilation
-PLA2 - eicosanoids --> vasodilation |
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What does the H2 receptor do
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-stimulates adenylyl cyclase - increases cAMP (vasodilation)
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What do H3 receptors do
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-causes decreased Ca influx into some cells
-function as feedback inhibitors, antagonizing effects mediated through H1 receptors |
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Cardiovascular actions of histamine
-which receptors |
-vasodilator of arterioles
-increases capillary permeability -minor positive chronotorpic, inotropic effects -stimulates axon refelxes -H1, H2, H3 |
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H1 receptor cardiovascular effects
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-rapid, short lived (endothelial cells, EDRF, eicosanoids)
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H2 receptor
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smooth muscle - slower, sustained
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H1 receptors are located where
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-large vessels (contracts)
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T/F - H1 receptors are responsible for increased capillary permeability
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-true
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How does histamine cause indirect CV actions
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stimulates axon reflexes - can amplify direct vasodilation by histamine
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What effect does histamine have on smooth muscle
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-contracts GI, bronchioles via H1 receptor
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What effect does histamine have on acid secretion
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-stimulator of gastric acid secretion (H2 receptor)
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What effects does histamine have on CNS
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-NT to increase alertness (H1)
-Pa, pain, AVP secretion (H1/H2) -inhibition of histamine release (H3) |
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What effect does histamine have on PNS
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-inhibits NE release from sympathetic neurons presynaptic H3 receptors
-enhances histamine's vasodilatory actions |
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Diphenhydramine:
-what is it -effects |
-ethanolamine (H1 antagonist)
-marked sedation, anti-motion sickness activity |
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Pyrilamine:
-what is it -effects |
-ethylenediamine (H1 antagonist)
-moderate sedation, component of OTC sleep aid |
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Cyclizine:
-what is it -effects |
-piperazine derivative (H1 antagonist)
-slight sedation, anti-motion sickness |
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Meclizine:
-what is it -effects |
-piperazine derivative (H1 antagonist)
-marked sedation, anti-motion sickness activity |
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Promethazine:
-what is it -effects |
-phenothiazine derivative (H1 antagonist)
-marked sedation, antiemetic, anti-muscarinic |
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Diphenhydramine:
-what is it -effects |
-ethanolamine (H1 antagonist)
-marked sedation, anti-motion sickness activity |
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Diphenhydramine:
-what is it -effects |
-ethanolamine (H1 antagonist)
-marked sedation, anti-motion sickness activity |
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Pyrilamine:
-what is it -effects |
-ethylenediamine (H1 antagonist)
-moderate sedation, component of OTC sleep aid |
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Pyrilamine:
-what is it -effects |
-ethylenediamine (H1 antagonist)
-moderate sedation, component of OTC sleep aid |
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Cyclizine:
-what is it -effects |
-piperazine derivative (H1 antagonist)
-slight sedation, anti-motion sickness |
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Cyclizine:
-what is it -effects |
-piperazine derivative (H1 antagonist)
-slight sedation, anti-motion sickness |
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Meclizine:
-what is it -effects |
-piperazine derivative (H1 antagonist)
-marked sedation, anti-motion sickness activity |
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Meclizine:
-what is it -effects |
-piperazine derivative (H1 antagonist)
-marked sedation, anti-motion sickness activity |
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Promethazine:
-what is it -effects |
-phenothiazine derivative (H1 antagonist)
-marked sedation, antiemetic, anti-muscarinic |
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Promethazine:
-what is it -effects |
-phenothiazine derivative (H1 antagonist)
-marked sedation, antiemetic, anti-muscarinic |
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Astemizole:
-what is it -effects |
-piperidine (H1 receptor antagonist)
-slight sedation, anti-motion sickness |
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Terfenadine:
-what is it -effects |
-piperidine (H1 receptor antagonist)
-lower incidence of sedation |
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Loratadine:
-what is it -effects |
-H1 recepto antagonist
-newer, longer action, little sedation |
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Which H1 antagonists are considered non-sedating
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-terfenadine
-astemizole -loratadine -fexofenadine **largely excluded from CNS b/c they are quaternary amines |
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What are the major side effects of terfenadine and astemizole
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-lethal polymorphic ventricular tachycardias at high doses OR when hepatic metabolism is impaired by: macrolide antibiotics, antifungals, other drugs
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Which H1 ant is given as a mild sedative
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-diphenhydramine, pyrilamine
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Which H1 ants are give for local anesthetic
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-promethazine, pyrilamine
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Which H1 ants are given for motion sickness
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-cyclizine, meclinzine due to anti-cholinergic effects
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Which H1 ants are given for anti-emetics
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-promethazine
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Which H1 ants are used for conscious sedation
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-promethazine and hydroxyzine
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T/F - the sedative effect from H1 antagonists is enhanced by opioid analgeics
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-true
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T/F - H1 antagonists used in dentistry help to reduce post-op nausea and vomiting
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-true
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Where is serotonin stored
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-platelets, neurons, GI tract in enterochromaffin cells
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What causes serotonin to be released
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-EC cells - mechanical stimulation, NE, vagal
-platelets - aggregation, degranulation -neurons -NT -carcinoid tumors - have enhanced release |
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Serotonin receptors (5-HT)
5-HT 1a,b,d,e,f 5HT 1c 5HT 2abc 5HT 3 |
-decreased adenylyl cyclase
-increased PLC, EDRF -increased PLC, increased Ca (contraction, platelet aggregation) -ligand gated cation channels |
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CV serotonin actions
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-direct vasoconstriction of vascular smooth mm (HT2)
-indirect vasodilation --> inhibits NE release (HT1) and endothelial release of EDRF, PGs (HT1) -platelet aggregation (HT2) -Bezold-Jarisch reflex |
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Explain the bezold-jarisch reflex
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-5HT3 receptor mediated reflex bradycardia due to stimulation fo sensory nerve endings
-causes inhibition of SNS -causes increased activity of cardiac vagus nerve |
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serotonin actions on smooth muscle
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-contracts GI and bronchioles
-diarrhea associated with carcinoid syndrome due to effects on GI smooth muscle |
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serotonin actions on nervous system
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-NT role
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Cyproheptadine:
-what is it -why it's prescribed -side effects |
-nonselective 5HT1 and 5HT2 antagonist
-treat carcinoid tumor symptoms -similar to H1 histamine receptor antagonists |
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Ketanserin:
-what it is -what it does -how it works |
-5HT2 selective (2A>2C)
-lowers arterial pressure in hypertensives -blocks HT2 receptors on vascular smooth mm and blocks alpha-1 adren recp on smooth mm (it is non-selective) |
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Ergot alkaloids
-LSD -ergonovine |
-5HT2 antagonist, VSM stimulant
-partial HT agonist, weak antagonist, used to dx vasospastic angina and control postpartum bleeding, has direct vasoconstrictor action (5-HT2) |
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methysergide
-mechanism -used to treat |
-partial agonist and antagonist at HT2 receptors, also blocks HT1 receptors
-VSM stimulant -carcinoid tumors |
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ergotamine
-mechanism -used to treat |
-partial agonist at HT2 receptors
-VSM stimulant -acute migraines, postpartum bleeding |
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sumatriptan
-mechanism -used for -how it works |
-5-HT1 agonist (b,d,f)
-inactive at other receptos -acute migraines, cluster headaches -activation of prejunctional HT1b/d receptors blocks trigeminovascular system |
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zolmitriptan differs from sumatriptan how
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-crosses BBB
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