Pharmacology of Histamine Flashcards
Where is histamine in the body?
all tissues
mast cells
basophils
Where is the H1 receptor found?
CNS
Smooth muscles
Blood vessels
sensory nerve endings
Where is H2 receptor located?
CVS
gastric mucosa
vascular smooth muscle
Where is H3 receptor found?
Presynaptic nerves in brain
airways and GI tract
Where is the H4 receptor located?
eosinophils, basophils, neutrophils, mast cells and CD4 T cells
skin nerve endings
Function of histamine
inflames local tissues and increases the blood flow
immediate hypersensitivity type I allergic reaction
Example of histamine agonist?
Betahistine (H1 agonist/H3 antagonist)
decreases symptoms of vertigo in Meniere’s disease
Adverse effects of betahistine
CNS: headache
GI: nausea and vomiting
List the 3 drug classes of H1 receptor blockers and state whether is sedating or non sedating
first gen - sedating
second gen - non-sedating
third gen - non-sedating
H1 receptor blockers do not antagonize the ________ of histamine to the H1 receptor, but bind to ________ sites to produce an opposing effect
binding
different
T or F: H1 receptor blockers are more effective in preventing than reversing symptoms
TRUE
List 3 examples of first gen antihistamines
diphenhydramine
dimenhydrinate
chlorpheniramine
List 3 examples of first gen antihistamines
diphenhydramine
dimenhydrinate
chlorpheniramine
Cons to first generation antihistamines
CNS penetration
disrupts REM
tachyphylaxis
dry mouth, blurred vision, orthostatic hypotension
