IL. Histamine Flashcards
2 things histamine is metabolized to?
mech of excretion?
N-methyhistamine
imidazole acetic acid
`
urinary excretion
wt is histamine synthesized from?
enzyme?
histidine
histidine decarboxylase
wt type of receptor is H1?
H2?
1 - Gq
2 - Gs
2 drugs causing release of histamine?
sucinylcholine
morphine
wr is histamine stored in GI?
2 things stimulating release?
ECL cells
Ach and gastrin
chief storage site of histamine?
3 immunologic stimulators of release?
IgE
PGs
Leukotrienes
where is histamine stored in the blood?
basophils
how do H1 and H2 receptors induce vasodilation?
H1 on endothelium release NO (immediate)
H2 on SM (slow and sustained)
hw do H1 and H2 receptors affect the heart?
inc rate and force of contraciton
H1 vasodilate –> reflex
H2 direct on cardiac muscle
action of histamine in lungs? wc receptor?
bronchoconstriciton
H1
aciton of histamine in gut? wc receptor?
inc gastric acid secretion H2
4 actions of histamine in neurons?
pruritus/itching
pain
increase wakefullness
inhibits appetite
wt is responsible for hives related to histamine? wt receptor?
inc capillary permeabity
H1 receptor
triple response to cutaneous histamine? cause?
red spot - vasodilaiton
flare – axon reflex and vasodilation
wheal – capillary permeability
H1 antagonist effect on: vasodilation permeability heart rate bronchoconstriction acid secretion pruritus flare
vasodilation - inhibits permeability - inhibits heart rate - partially blocks bronchoconstriction -- little effect acid secretion - no effect pruritus - some relief flare - supress axon reflex and dilation
2 other actions of first H1 antagonists? most effective?
antimuscarinc effects
motion sickness
promethazine
do first or second generation H1 antagonists have more AEs?
first
4 AEs of first generation H1 antagonists?
CNS stimulaiton (at conventional doses)
CNS depression (at theurapeutic doses)
antimuscarinic (dry mouth)
GI
wc second gen H2 antagonist has AEs?
cetirizine
5 indications for H1 antagonists?
allergy bronchial astham anaphylaxis motion sickness sedation
action of H2 antagonists?
dec gastric acid secretion
wc H2 antagonist inhibits CYP450?
cimetidine
2 indications for H2 antagonists?
ulcer
GERD
wc H1 antagonists is metabolized by Cyp3A4?
loratadine
where are anti-H1s metabolized?
H2?
liver
kidney
2 things reducing anti-H1 activity?
alcohol and CNS depressents
MOA of cromolyn and nedocromil?
inhibit degranulation of mast cells
