drug therapy to decrease histamine effects and allergic response Flashcards
describe histamine (H1)
-1st cemical mediator released in immune and inflammatory response
-found in mast cells and basophils
-released in response to stimuli (allergic reactions, cellular injury)
-after its release, its target cells are in the blood vessels, respiratory, and GI tract
describe the allergic response
when histamine stimulates its receptors, what happens?
-contraction of smooth muscles in resp tract (can experience resp distress/wheezing)
-stimulation of vagus nerve (coughing, bronchoconstriction)
-increased permeability of veins and capillaries (edema)
-increased secretion from mucus glands
-stimulation of peripheral nerve endings (pain and itching)
-increase secretion of gastric acid
-increased HR and force
describe hypersensitivity reactions
-involves an exaggerated allergic response
-can cause tissue damage or serious illness (anaphylactic reactions)
-caused by an abnormal immune reaction
-four types based on producing mechanism
-types I,II, III are antibody mechanisms
-type IV is antigen specific T cells
describe type I hypersensitivity
immediate hypersensivitity
-occurs within minutes
-IgE induced mast cell activation
-usually after 2nd or later exposure
-mild to severe
mild: itching, rhinitis
severe: anaphylactic-respiratory distress, cardiac collapse, life threatening
describe type II hypersensivitity
cytotoxic
-mediated by IgG or IgM
-generates direct damage to cell surface
-blood transfusion reactions
-hemolytic disease of newborns, hemolytic anemia
describe type III hypersensivitity
immune complex
-mediated by IgG or IgM
-forms antigen-antibod complexes and acute inflammatory reaction in tissue
-serum sickness (excess antigens and antibodies building up -> can cause permanent tissue damage)
pretty rare -> usually seen after antibody transfusion or as a reaction to some medications
describe type IV hypersensivitity
delayed hypersensivitity
-cell mediated response (not immediate)
-sensitized T lymphocytes react with antigen to cause inflammation
-tuberculin test, contact dermatitis, graft rejection
true or false?
histamine is the first chemical mediator released during inflammatory response
true
histamine is the first chemical mediator released during immune and inflammatory response. it is synthesized and stored in most body tissues. especially ones exposed to the outside such as eyes, nose, mouth, and GI track
true or false
four classifications of hypersensitivity reactions exist
true
four classifications of hypersensivitity reactions exist: type I (immediate), type II (direct damage to cell surfaces), type III (formation of antigen-antibody complexes), and type IV (delayed hypersensivitity)
what is allergic rhinitis
inflammation of nasal mucosa caused by type I reaction to inhaled allergens
what are some symptoms of allergic rhinitis
-nasal congestion
-itching, sneezing
-watery drainage
-itching of throat, eyes, and ears common
what are two types of allergic rhinitis
-seasonal disease (AKA hay fever)
-perinnial disease
describe seasonal disease (AKA hay fever)
response to airborne pollens
describe perinneal disease
-response to nonseasonal allergens
-dust mites, molds
-animal dander
describe allergic food reactions
-immune response to ingestion of a protein
-shellfish, fish, corn, seeds, bananas, egg, milk, soy, peanut, tree nuts
-higher risk of triggering anaphylaxis
-children allergic to milk, eggs, wheat, soy may outgrow their allergy, no known preventative
describe contact dermatitis
-type IV reaction from direct contact with antigen
-poison ivy, cosmetics, metals
-affected skin is inflamed, warm , swollen, itchy
-blisters may form, drain, and become infected
-usually occurs 24hrs after contact
describe drug reactions
-any drug can cause a reaction
-any body tissue may be involved
-symptoms vary but may include.. skin rash, itching, fever, hematologic or hepatic reactions
-may occur 7-10 days after initial exposure
-resolves after drug is discontinued
true or false?
allergic rhinitis is caused by type III sensitivity
false
allergic rhinitis is inflammation of nasal mucosa caused by a type I hypersensitivity reaction to inhaled allergens
what do antihistamines do?
relieve symptoms but do not relieve hypersensitivity
what are antihistamines used for?
-allergic rhinitis
-anaphylaxis
-allergic conjunctivitis
-drug allergies, pseudoallergies
-blood/blood product transfusion
-dermatologic conditions, etc
give an example of first generation H1 receptor anatgonists
diphenhydramine
what do first generation H1 receptor anatgonists do?
-prevent/reduce most physiologic effects that histamine produces at receptor sites
-inhibit smooth muscle constriction in blood vessels, rep, GI tract
-decreases capillary permeability
-decrease salivation and tear formation
describe the action of first generation H1 receptor anatgonists
occupy same receptors as histamine which prevents histamine from reaching target
describe the use of first generation H1 receptor anatgonists
-allergic reactions
-motion sickness
-insomnia
-children may experience paradoxical effect
what are some adverse effects of first generation H1 receptor anatgonists
-CNS depression
-anticholinergic effects
what are some contraindications of first generation H1 receptor anatgonists
-narrow angle glaucoma
-BPH
what are some nursing considerations with first generation H1 receptor anatgonists
-use caution in older adulta, may cause confusion
-may thicken secretions
describe patient education with first generation H1 receptor anatgonists
-take med before exposure to allergen
-tolerance to drowsiness in few days
-avoid taking with alcohol
-avoid accidental OD
give examples of second generation H1 receptor antagonists
-fexofenadine
-loratadine
-cetirizine
what do second generation H1 receptor antagonists do?
-does not readily enter the brain from the blood
-bind preferentially to peripheral rather than central H1 receptors
-replacing first generation H1
-have mild beneficial effect in chronic asthma
describe the action of second generation H1 receptor antagonists
occupy the same receptors as histamine which prevents histamine from reaching target
describe the use of second generation H1 receptor antagonists
-seasonal allergic rhinitis
-minor allergies
-itching
what are some nursing cosiderations with second generation H1 receptor antagonists
-safer in older adults
-use caution with renal failure
describe patient education with second generation H1 receptor antagonists
-take med before exposure to allergen
-teach proper use of nasal spray if needed
-avoid taking with alcohol
-avoid accidental OD
when explaining the options for antihistamines, the nurse explains that second generation H1 receptor antagonists differ from first generation H1 receptor antagonists by…
A) cause greater CNS sedation
B) are available by prescription only
C) are more cost effective
D) do not cross blood brain barrier
D) do not cross blood brain barrier
second generation H1 receptor antagonists like fexofenadine do not enter the brain reducing the side effect of sedation
