Allergic rhinitis and antihistamines Flashcards
what antibody is associated with hay fever?
Ig E mediated reaction
major symptoms?
rhinorrhoea (runny nose)
nasal itching
congestion
sneezing
classification of persistent hay fever?
majority of the week more than 28 days at a time
classification of intermittent hay fever?
<4 days a week, <28 days at a time
3 pharmacotherapy options for hay fever?
mast cell stabilisers
steroids
antihistamines
how does use of sodium cromoglicate work?
decreases release of histamine from mast cells
best to use before symptoms
typically eye drops OTC
steroid used for hay fever?
beclomethasone nasal spray
only 3 months in a row - causes rebound congestion
what type of antihistamines are used for hay fever?
H1 receptor antagonists
1st generation = sedating
2nd generation = non-drowsy
how is histamine synthesized in the body?
HDC enzyme causes decarboxylation of histidine amino acid
effect of histamine in the skin?
triple response of lewis
1 red line
2 flare
3 wheal
effect of histamine on the heart? (H1 receptors)
increased force of contraction due to Ca2+ influx
increased HR - depolarization of SA node
effect of histamine on the heart? (H2 receptor)
slows AV conduction, increases automaticity, arrhythmia
effect on lungs of histamine on H1 receptor ?
bronchoconstriction - increased mucus viscosity
stimulation of vagal sensory nerve endings - cough
effect on lungs of histamine on H2 receptor ?
slight bronchodilation - increased mucus secretion
why are 1st generation antihistamines sedative?
lipid soluble, CNS penetration, BBB transfer
