Term
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Definition
present in many tissues
synthesized from histidine by L-histidine decarboxylase |
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Term
| Main histamine storage site |
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Definition
| Mast cell granules, release when mast cells are activated by specific allergens |
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Term
| Physiological events in response to histamine |
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Definition
smooth muscle relaxation/contraction
blood vessel dilation
increased capillary permeability
wheal and flare |
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Term
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Definition
Agonism causes an increase in intracellular calcium by activation of PLC
This is the most active receptor for histamine actions in smooth muscles
vasodilation, bronchoconstriction, +inotropic and chonotropic on heart
CNS stimulation/depression, motion sickness |
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Term
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Definition
| Mepyramine, chlorpheniramine, triplodine |
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Term
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Definition
agonists cause increase in IC cAMP via Gs receptors
Stimulates gastric secretion, regulates blood pressure and CNS functions |
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Term
| H-2 selective antagonists |
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Definition
| Cimetidine, ranitidine, famotidine, nizatidine |
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Term
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Definition
agonists cause a decrease in calcium influx into the cells
Involved in feedback inhibition of NT release |
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Term
| H-3 selective antagonists |
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Definition
| thioperamide, clobenpropit |
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Term
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Definition
agonists cause eosinophil and mast cell chemotaxis mediated by Gi/o
Particularly treated in the case of rheumatoid arthritis and IBD |
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Term
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Definition
First generation: rapid onset, 4-6 hour duration
Second generation:rapidly absorbed and duration of 4-24 hours
allergic conditions
motion sickness/vertigo/sedation |
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Term
| Would you use an H1 blocker in acute anaphylaxis? |
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Definition
| NO, because histamine is only one of the mediators released in a severe attack and antihistamines don't treat the underlying cause |
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Term
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Definition
Sedation, GI effects, dry mouth (muscarinic side effect)
CNS stimulation with OD |
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Term
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Definition
| rapidly absorbed after oral intake, with peak levels in 1-3 hours and must be dose adjusted in renally impaired patients |
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Term
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Definition
Inhibit gastric acid secretion, especially at night, thus dosing once daily after dinner can aid in ulcer healing
Ulcer healing/GERD/prophylaxis |
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Term
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Definition
| used to treat moderate to severe cases of hives |
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Term
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Definition
usually minimal, may induce diarrhea, constipation, headache, drowsiness, fatigue, and muscle pain
Cimetidine May interfere with estrogen metabolism and cause gynecomastia/impotence
CimetidineInhibits CYPs, more drug-drug interaction |
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