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49 Cards in this Set

  • Front
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Histamine Structure
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Histamine-in general
autocoid and neurotransmitter
HA-peripheral effects
synthesized and stored in mast cells and chromaffin cells
MAST: IgE-related allergic response
GI: gastric acid secretion
HA-neurotransmitter
overall alertness, general psychiatric functions (emotions, appetite) BLOCK=sedation
H1 Receptors
Where? periphery and CNS
Modulated? G-alpha-Q => PLC, IP, DAG, ^ Ca release
H1 Mediates?
typical allergic response-immediate, primary
ALSO: contraction of smooth muscles, asthma, diarrhea
**epithelial contraction= redness, swelling, edema
H2 Receptor
where? periphery and CNS
Mediated? G-alpha-S =>Aden cyclase, cAMP, PKA
H2 Receptor effects
GI: acid secretion (parietal cells)
vasodilation
CNS-unknown
H3 Receptor
where? CNS only
mediated? G-alpha-I=> decreases AC, cAMP, PKA
**negatively regulates NT release
H4 Receptor
where? CNS and periphery
mediated? G-alpha-S, AC, cAMP
**leukocytes and bone marrow = immune response
HA chemistry
lone pairs on nitrogen, fairly basic
Histadine Structure
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HA Metabolism-
Histadine + ...
histadine decarboxylase
Histamine-
Breakdown (1st)
histamine methyl transferase--adds methyl where?
HA-
Breakdown (2nd)
diamine oxidases (and others)
end product of HA metabolism
1-methylimidazole acetic acid
**diagnostic urine metab--for allergic rxns
HA storage
in storage granules: + form ionic bonds with - acidic groups
**heparin & chondroitin (-)
HA activation-in general
positively charged drugs displace HA and goes on to activate receptors
**esp. alkaloid drugs like morphine, piperidines, amine, ammonium
HA activation step 1
IgE on mast cells are receptors for allergens
HA activation step 2
IgE receptor is activated by allergen
**DAG & IP3 -release Ca, HA released
HA activation step 3
Release Ca from ER-facilitates degranulation, HA released
***can be blocked by antihistamines
HA block (1)
-block increase in IP3--cromolyn sodium
cromolyn sodium structure
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HA block (2)
-increase in cAMP=relax the secretory response of mast cells
EX: beta agonists-relax smooth muscle
PDE inhibitors
block conversion of cAMP to AMP--imp for asthma tx
immediate release from mast cells
HA, heparin, chondroitin, TNF
5 minutes-released from mast cells
prostaglandins, leukotrienes, PAF
1 hour-released from mast cells
cytokines (interleukins)
DRUGS
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H1 Receptor 1st generation antagonists
diphenhydramine, chlorpheniramine, cyclizine
H1 Receptor 2nd generation antagonists
meclizine, terfenadine, fexofenadine, loratadine
H1 Receptor 3rd generation antagonists
desloratadine, hydroxyzine, cetirizine
H2 Receptor antagonists
cimetidine, ranitidine, famotidine, nizatidine
Diphenhydramine structure
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Dimenhydrinate structure-chlorotheophylline salt of benadryl
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all 1st gen HA antagonists
1. non-selective: also block ACh muscarinic, alpha adren (dec. BP), 5HT
2. dec. gi contract
3. other CNS mech and dec. nausea/vomiting (** X BBB)
chlorpheniramine structure
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**S (+) =ACTIVE
R (-) =INACTIVE, contributes to SE's, chlor-trimeton=racemate
cyclizine structure
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meclizine structure
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Meclizine in general
add'l Ph ring, binds to albumin, retained in blood
-hydrophobic aromatic & H-bonding
LESS: X BBB, sedation
INCREASED: t1/2
stablized mast cell HA granules
terfinadine structure
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** racemic & is prodrug
fexofenadine structure
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*active metabolite
Terfinadine problems
Block metab by P450?
= cardiac arrhythmias
(macrolide ABX, antifungals, grapefruit juice)
loratadine structure
-comp to chlorpheniramine
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desloratidine structure
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hydroxyzine structure
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cetirizine structure
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*active metabolite of hydroxyzine
general structure of H2 receptor antagonists
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**x,Y= N, S, O
H2 recep. antagonists
1. decrease gi acid secretion
2. receptors in blood vessels
3. many interactions with cimetidine and ranitidine