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26 Cards in this Set
- Front
- Back
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main cells that contain histamines
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mast cells and basophils
enterochromaffine-like cells in gastric mucosa certain neurons in CNS |
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where are there high concentrations of mast cells and basophils
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lungs
skin GI tract |
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what stimulates histamine release?
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IgE plus antigen
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what are all histamine types and what are their MOA
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H1 - coupled to Gq
H2 - coupled to Gs H3 - coupled to Gi H4 - coupled to Gi |
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where are all histamine types located
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H1-H4 - brain
H1 - SMC, vascular endothelium, sensory neurons (what we will study) |
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what are the actions of the H1 receptor on target tissue...
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SMC of bronchioles and SMC of GI tract -
Gq coupled to stimulate to contract On vasculature - cause endothelium to release NO and cause vascular SMC to relax also contracts endothelial cells of capillaries and increase capillary resistance |
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All actions of histamines pertaining to us - 5
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constrict bronchiole SMC
constrict GI SMC Relax vascular SMC Increase capillary permeability stimulate nerve ending - itch |
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Are antihistamines useful in treating bronchoconstriction in asthmatics?
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no because blocking the action of histamine will not undo the adrenergic tone - which is the driving force
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what are the 1st generation antihistamines
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chlorpheniramine
dimenhydrinate DIPHENHYDRAMINE hydroxyzine MECLIZINE promethazine |
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what are the 2nd generation antihistamines
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FEXOFENADINE
LORATADINE desloratadine cetrizine levocetrizine azelastine |
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What is the role of histamines in allergic reactions
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allergic rhinitis
allergic urticaria anaphylaxis |
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how does allergic rhinitis occur?
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histamine release due to allergen in nasal mucosa -
leads to NO induced vasodilation and increased vascular permeability |
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how does the wheal and flare occur in acute urticaria?
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NO induced vasodilation - red spot
increased vasc perm - wheal axon reflex - peripheral vasodilation - flare |
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discuss antihistamines and anaphylaxis tx...
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antihistamine is not too good at treating this - effective but not quick enough for anaphylaxis
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effect of antihistamine on brain
2 major ones |
Histamine on hypothalamus causes wakefullness
So... antihistamine causes CNS depression and sedation/drowsiness also antihistamine blocks h1 AND M receptors in vestibular apparatus to prevent motion sickness |
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what is difference between 1st and 2nd generation antihistamines
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1st gen - shorter duration of action
the have high sedation effects, antiemetic effects(prevent motions sickness) and anti muscarinic effects 2nd generation - long lasting, low sedation, no antiemetic and very low antimuscarinic effects |
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clinical uses of 1st and 2nd generation antihistamines
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allergic rhinitis
conjunctivitis urticaria angioedema - supportive to epi serum sickness - epi is drug of choice |
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what is a topical antihistmaine that we specifically talked about
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diphenhydramine
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what is the clinical use of diphenhydramine?
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topical for temporary relief of pruritus(itch) and pain - minor burns, sunburn, minor cuts, insect bites
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clinical use of specifically 1st generation antihistamines
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sedation, hypnosis - sleep aid
motion sickness common cold parkinsonism - anticholinergics (fair) |
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side effects of 1st generation antihistmaines
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CNS - sedation, dizziness, fatigue
Atropine-like effects - dry mouth, blurred vision, dry eyes, urinary contact dermatitis - topical use teratogenicity - MECLAZINE |
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which drug has a potential teratogenicity?
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meclazine, among other antihistamines
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how bad can the antimuscarinic effects of antihistamines get?
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acute poisoning is like atropine poisoning -
hallucinations, excitement, ataxia, incoordination, convulsions |
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how do we treat the anticholinergic toxicity of antihistamines or atropine?
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physiostigmine
if convulsing - diazepam |
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what is cromolyn used for?
how is it given |
nasal spray and opthalmic preperation - prophylactic for seasonal rhinits
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what kinds of agents can we use to treat seasonal rhinitis
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cromolyn
alpha adrenergic agonists - pseudoephedrine and phenylephrine intranasal corts luekotriene inhibitors |
