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27 Cards in this Set
- Front
- Back
drug list
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learn em
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where is histamine at?
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they're in mast cells (organs) and basophils (in blood cells) which sit in lung, skin, intestinal mucosa: first defense
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how do you make histamine?
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histidine ---his decarboxylase (PLP dependent [vit 6])--> histamine
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When do you release histamine?
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injury
allergy (type 1 hypersensitivity via IgE) drugs/foreign compounds |
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So to get bad reaction you have the two exposures to ___ the mast cells
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prime them. Your ab are ready and attached so if ag happens, you go crazy on it.
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What all are mast cells releasing?
If you blocked histamine release would that stop all the effects of mast cells? |
histamine
prostaglandins leukotrienes chemotactic agents no. |
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What if you combo'd histamine and leukotriene blocking?
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it will work better
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there are ___ different histamine receptors
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three or four.. he contradicted it
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H1 receptor
signaling pathways |
this is the one that we're talking about- intestinal, bronchial, smooth muscle, endothelium, brain
this one is DAG/IP3 |
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what effects does histamine have?
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hypotension in the beginning since it's all dilated and widening of endothelial gaps and fluid moves out to interstitial space and edema
respiratory effects: H1 mediated constriction GI effects: HI smooth muscle contraction |
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how does histamine affect stomach?
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gastrin -> ECL cells which use histamine to make parietal cell to release stomach acid
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histamine and wakefulness and appetite
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hist increases wakefulness and inhibits appetite
if you have inhibitor of H1Receptor, may have aggression and locomotion. Antihistamines can also. |
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how do antihistamine drugs work?
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inverse agonists of H1- bind to receptor in inactive state
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popular antihistamine: first generation
side effect cleared by what does it treat mechanism work best if |
diphenhydramine
can have sedation side effect cleared by CYP450 inhibit capillary permeability, not as good for lungs inverse agonist given before the exposure |
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What do you notice about cough medicines?
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they always have an antihistamine in them, but it's kind of bad because they'll dry out the airways even if they treat symptoms.
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What is off target effect of diphenhydramine?
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anticholinergic (this is muscarinic ACh too)
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Another antihistamine often used with cold products, motion sickness, nausea/vomiting
what is this drug like? |
promethazine
inverse agonist with significant central anticholinergic, sedative, antiemetic effects works quickly, cleared quickly |
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an antihistamine for antidepressant
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doxepin
very few side effects, also sleep aid |
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second generation: original that's no longer available
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terfenadine
withdrawn because cardiac arrhythmia metabolized by CYP3A4, so CYP inhibitors affect toxicity |
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What are the new 2nd gen antihist's? 3+
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fexofenadine: minimal sedation and antimuscarinic activity
cetirizine: H1 blocker. Don't go through BBB so sedation is limied, but drowsiness still serious. loratadine: oral, non-sedating H1 blocker- this one IS CYP450 metabolized so drug interactions should be noted desloratadine is getting read-> it becomes loratadine |
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excretion patterns of antihistamines
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first gen were metabolized in the liver by CYP450's like CYP2D6
2nd gen go in urine unmetabolized except loratidine which is P450 activated pro-drug |
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drug interactions with antihist
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other sedating things like barbituates but more commonly alcohol
older people don't metabolize as well, so. |
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So should all pts be switched to second gen drugs?
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not necessarily
1st gen is cheaper, well-established, know what to expect |
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how are the antihist acting as an antiemetic?
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the regions in brain has a lot of H1 receptors.
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What else is antihist used for?
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insomnia
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When would you not want to use antihist?
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type I hypersensitivity caused by another drug
don't affect asthma not useful in colds and flu |
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Would diphenhydromine help stomach ulcers?
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well not really because parietal cells have H2 and these are for H1.
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