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Anes. Pharm I Test 3

Itching to Anaphylaxis

What are the roles and functions of histamine in the body? mediator of allergic reactions and inflammatory processes, affects gastric secretions, neurotransmitter, neuromodulator
Is histamine active or inactive in its bound form? inactive
What cell types store the bulk of bound histamine? basophils and mast cells; enterochromaffin-like cells
What is the major pathophysiologic cause of histamine release? immunologic; cells have IgE antibody attached to membrane, when antigen is exposed to cells degranulation occurs causing release of histamine and other mediators
Negative feedback of H2 receptor types is found in the skin and basophilic but NOT found where? in the lungs - bronchoconstriction will continue unless we intervene
Which subtype of histamine receptors are similar to muscarinic receptors? H1
Which subtype of histamine receptors are similar to 5HT1 receptors? H2
Where are H1 receptors located? postsynaptic in the brain, endothelium, smooth muscle cells, nerve endings (brain)
Where are H2 receptors located? postsynaptic in the brain, gastric mucosa, cardiac muscle cells and some immune cells
What does activation of H1 receptors cause? bronchoconstriction, slowed conduction throughout the AV node, and coronary artery vasoconstriction
What does activation of H2 receptors cause? CNS stimulation, increased myocardial contractility and HR, bronchodilation, increased secretion of H= ions by gastric parietal cells
What does activation of H3 receptors cause? decreased NE release, decreased synthesis and release of histamine
Where are H3 receptors located? presynaptic postganglionic sympathetic nervous system
Where are H4 receptors located? bone marrow and blood
Amine drugs can compete with histamine for sites within cells and displace the histamine. This is not an immunologic reaction. What are some examples of drugs that can do this? morphine and tubocurarine
A patient on chronic H2 blockers will probably have which other receptor blocked as well? H3 - if they have histamine release it will be massive because negative feedback system inhibited
True or false: the bronchoconstriction caused by H1 receptors typically wins out over the bronchodilation caused by H2 receptors. True! This is especially true for asthma patients who are 100x to 1000x more sensitive to histamine
True or False: histamine receptor blockers inhibit the release of histamine. FALSE! they do NOT inhibit the release of histamine
Which drugs are H1 blockers? diphenhydramine (benadryl), dimenhydrinate (dramamine), meclizine (bonine), promethazine (phenergan)
Which drugs are H2 blockers? cimetidine (tagamet), famotidine (pepcid), ranitidine (zantac)
What is the mechanism of action of H1 blockers? prevent activation of H1 receptors through competitive antagonism with histamine & may even push histamine off the receptor
What other types of receptors may be activated by H1 blockers? muscarinic cholinergic, 5HT3, alpha-adrenergic
What is the mechanism of action of H2 blockers? prevents increase in intracellular cAMP which would activate the proton pump of the gastric parietal cells to secrete H+ ions
Which drug is a physiologic antagonist of histamine? epinephrine - it is the anaphylaxis treatment drug of choice
What drugs prevent the release of histamine? cromolyn and beta2 agonists (albuterol)
Drug reactions are frequent in anesthesia, though only about what % are true allergic reactions? 10%
What are some risk factors for allergic reactions/anaphylaxis? receiving IV drugs, hx of allergies or atopy, asthma, previous reactions, women, previously received anesthetic
Which muscle relaxant drugs are the worst offenders for allergic reactions? Succinylcholine and Rocuronium (usually non IgE)
What is the treatment for anaphylaxis? remove offending agent, agressive airway management, circulatory management (fluids, epi, vaso), stop anesthetic agents, give antihistamines and glucocorticoids
In a review of deaths related to anaphylaxis, an overdose of this drug was actually implicated as attributing to death. epinephrine
What are some prevention strategies for anaphylaxis? avoid risky patterns of practice (take careful history), intradermal skin testing, RAST test, leukocyte histamine release test, pharmacologic prophylaxis (H1 & H2 blockers & steroids)
Created by: Mary Beth



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