ENT-2 Flashcards
Where is histamine stored?
Mast cells- tissue
Basophils (in granules)- Blood
Where are H1 receptors?
Smooth muscle
Endothelium
CNS
Where are H2 receptors?
Gastric parietal cells
cardiac muscle
mast cells
CNS
Where are H3, H4 receptors?
Importance?
H3- CNS, presynaptic
H4- Hematopoetic origin
*No drugs target
What are the effects of H1 receptor agonism?
Primary responsible for histamine’s allergic effects
Upregulated on endothelial cells increase vascular permeability
Copious watery rhinorrhea
Present on nociceptive nerve fibers to induce itching sensation
What are the effects of H2 receptor agonism?
Stomach acid production
Vasodilation and cardiac effect in anaphylaxis
What is the effect of H4 receptor agonism?
Induction of cellular shape change, chemotaxis
Secretion of cytokines and upregulation of adhesion molecules
Compare H1/H2 receptor time to effect
H1 receptors have higher affinity -> rapid and short-lived vasodilation -> lower sys BP
H2 receptors-> more slowly and sustained
What are the cardiac effects of H1 activation?
Increases cardiac force of contraction and HR
Directly slows AV (Atrioventricular) conduction (via H1) arrhythmias
+ inotrope
+ chronotrope
-dromotrope
What is the triple response of Lewis
Effects of Histamine intradermal:
Localized red spot – a few mm ~1min
Brighter red flush or “flare” – 1cm – developing more slowly
Wheal – 1-2min
What is the effect of histamine at peripheral nerve endings?
Epidermis -> itch
Dermis -> pain or pain accompanied by itching
What are the risk factors for allergic rhinitis?
Family history Elevated IgE levels Higher socioeconomic class Positive skin test results Emigration into a Western industrialized environment
What are the sequelae of allergic rhinitis?
Sinusitis, obstructive sleep apnea
Otitis media, and nasal polyposis
What are the 1st line pharmacotherapies for allergic rhinitis?
Corticosteroids – nasal spray (NS)
Antihistamines – PO or NS
What are the second line treatments for allergic rhinitis?
Decongestants Mast cell stabilizers Leukotriene receptor antagonists Antimuscarinic (anticholinergic) agents Saline Monoclonal antibody