Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

27 Cards in this Set

  • Front
  • Back
What cells of the bodies release histamine?
Mast Cells
What are the various types of histamine antagonists?
H1 receptor antagonists - antiallergy drugs, anti-emetics, and vertigo treatment
H2 receptor antagonists - Anti-acid
H3 receptor antagonists - tricked you! no drug
H4 receptor antagonists - we still don't know what the fuck this is!
Besides histamine what are some other enhancers of gastric acid secretion?
gastrin and vagal stimulation
What is the H3 receptor for?
Histamine can function as a neurotransmitter through the H3 receptor and cause its own inhibition by binding to the presynaptic H3 receptors
What are the pathophysiological actions of histamine?
Seasonal Allergies
Duodenal ulcers - larege release of histamine in the stomach
Systemic Mastocytosis - mast cell infiltration of tissue with massive histamine release
Gastrinoma (Zollinger-Ellison Syndrome) - tumor that secretes gastrin
What amino acid is used to make histamine?
How is histamine metabolzed?
P450 system 2 pathways:
Methylation to N-methyl histamine (N-methyl transferase) then to N-methyl imidazoleacetic acid (monoamine oxidase) and elimination in the urine
Undergo oxidative damination to imidazoleacetic acid (diamine oxidase) then ribosylation to imidazoleacetic acid riboside also renally eliminated in urine
What are the messenger systems of the various histamine receptors?
H1 - Gq PLC to increase intracellular Ca leading to ca calmodulin MLCK and contraction (smooth muscle effect) or Ca calmodulin to activate NOS smooth muscle relaxation
H2 - Gs coupled to Adenylate Cyclase increasing cAMP. increase in cAMP activating PKA inactivating MLCK relaxation of smooth muscle or int he heart increasing PKA increasing open Ca Channel causing myocyte contraction
H3 coupled to Gi/o N-type voltage gated Ca channel and reduces Ca influcs and inhibits release of presynaptic transmitter
H4 coupled to Gi/o in mast cells and eosinophils and trigger calcium mobilization
Where are H1 receptors found?
Smooth muscles, endothelial cells, and in CNS
Within the bronchial tree causes smooth muscle constriction through PLC
Within blood vessels causes vasodialtion through NOS pathway
Within endothelial cells causes contraction leading to vascular leak and edema
Within peripheral nerve endings, causes pain and itching
within CNS causes allergic rhinitis and motion sickness
Where are H2 receptors found?
GI parietal cells, vascular smooth muscle cells, cardiac cells
Within GI Parietal cells regulates gastric acid secretion
Within vascular smooth muscle vasodialtion from cAMP
within the heart cAMP mediated contraction
Where are there both H1 and H2 receptors?
The cardiac cells:
H2 mediate both ionotropy and chronotropy
H1 receptors are in the AV node and slow conduction
Where are H3 receptors found?
Mostly CNS and Some peripheral nervous system
Can act as a neurotransmitter in feedback inhibition of histamine synthesis and release
May also control other neutransmitters
Where are H4 receptors found?
highly expressed in bone marrow and white blood cells
Important for mast cell chemotaxis
What is meant by the triple response to Histamine (aka "Triple response of Lewis")
It is a test for allergies using histamine (all through H1 receptor) which causes following subdermal injections:
Red spot - direct vasodilation effect (H1 mediated NO)
Flare - indirect vasodilation (activated sensory neuron axonal reflex)
Wheal - Increase in capillary permeability with accumulation and edema
What are two groups of substances that can cause degranulation and release of histamine?
IgE-antibody induced releasers
Non-immune releasers
what is the source of redman's syndrome and what is the instigating agent?
flush and red from vasodilation due to histamine related reactions caused by vancomycin IV administration
What are some drugs that inhibit the release of histamine?
Cromolyn Na
What are some causes of non-immune release of histamine?
Aspirin or NSAIDs
Morphine or other opioids
Polymixin B
X-ray contrast media
Succinylcholine, d-tubocurarine, compound 48/80
Anaphylatoxins - C3a and C5a
Cold or solar exposure leading to itching and urticaria
What are the pharmacological effects of histamine?
Mild allergic to anaphylaxis (both involve H1 and H2 receptors):
Dilation of small blood vessels --> flushing (H1 response)
Decreased TPR and BP (H1 initial and H2 sustained)
Increased Capillary permeability, edema (H1 response)
What are the histamine related drugs?
Mast Cell stabilizers (Cromolyn Na, nedocromil-tilade, albuterol)
H1 Receptor Antagonists (1st and 2nd generation)
H2 Recpetor Antagonists (ranitidine, Cimetidine)
What are the the various types of H1 receptor antagonists and how do they function?
First Generation were sedating due to CNS penetration
Second generation drugs are nonsedating due to inability to penetrate CNS
What are the important first generation H1 antagonists?
Diphenhydramine (benedryl) - prototype
Promethazine - for motion sickness
Cyclizine, Meclizine - motion sickness and vertigo
What are the uses of generation 1 H1 antagonists?
Adjunctive to anaphylaxis
Motion sickness
Local anesthetic
What are some adverse effects of First generation H1s?
Allergic reaction with topical use
Peripheral antimuscarinic effects (atropine like) - dry mouth, blurred vision, constipation, urinary retention
What are the uses and types of second generation drugs?
Antiallergy uses
Cetirizine (zyrtec)
Fexofenadine (allegra)
Loratadine (Claritin)
Desloratidine (clarinex) -metabolite of loratadine
Loratidine - half dose for Hive tx
Azelastin (intranasal spray)
What are the adverse effects of second generation H1 antagonists?
Cardiac K channels causing prolonged QT with resultant torsades de pointes - tx with?? (Mg!)
Cetirizine appears to have CNS and sedative actions
erythromycin and ketoconazole inhibit the metabolism of fexofenadine and loratadine
What are the pharmacokinetics of the second generation of H1 antagonists?
excreted in mainly unmetabolized forms
Cetirizine and loratadine primarily excreted in urine
Fexofenadine excreted in feces
all drugs induce the cytP450