drug therapy to decrease histamine effects and allergic response Flashcards
what is histamine
1st chemical mediator released, 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(eyes), respiratory(lungs) and GI tract
when histamine stimulates its receptors what happens
contraction of smooth muscles in respiratory tract(respiratory distress), stimulation of vagus nerve, increased permeability of veins and capillaries(edema), increased secretion from mucus glands, stimulation of peripheral nerve endings, dilation of capillaries in skin, increase secretion of gastric acid, increased heart rate and force
hypersensitivity reactions involves
an exaggerated allergic response (anaphylactic)
hypersensitivity reactions can cause
tissue damage and serious illness
hypersensitivity reactions are caused by
abnormal immune reaction
four types of hypersensitivity based on the producing mechanism
types I,II,III are antibody molecules, type IV are antigen specific T cells
type 1 hypersensitivity or immediate hypersensitivity is what
occurs within minutes, IgE induced mast cell activation, usually after 2nd or later exposure, mild to severe (mild= itching, rhinitis/ severe= anaphylaxis- respiratory distress cardiac collapse, life threatening
type II hypersensitivity or cytotoxic
mediated by IgG or IgM, generates direct damage to cell surface, blood transfusion reactions, hemolytic disease of newborns/ hemolytic anemia
type III hypersensitivity or immune complex
mediated by IgG or IgM, forms antigen(bad guy)-antibody(good guy) complexes (acute inflammatory reaction in tissue), serum sickness
type IV hypersensitivity or delayed hypersensitivity
cell-mediated response, sensitized T lymphocytes react with antigen to cause inflammation, tuberculin test, contact dermatitis, graft rejection
T or F. 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
T or F. four classifications or hypersensitivity reactions exist
true; Type I(immediate), II(direct damage to cell surfaces), III(formation of antigen-antibody complexes), IV(delayed hypersensitivity)
allergic rhinitis is what
inflammation of nasal mucosa caused by type I reaction to inhaled allergens
s/sx of allergic rhinitis
nasal congestion, itching, sneezing, watery drainage, itching of throat, eyes, ears
seasonal disease of allergic rhinitis
aka hay fever, response to airborne pollens
perennial disease of allergic rhinitis
response to nonseasonal allergies, dust mites/ molds, animal dander
allergic food reactions
immune response to ingestion of a protein
what are high risk foods that could trigger anaphylaxis
shellfish, fish, corn, seeds, bananas, egg, milk, soy, peanut, tree nuts
children allergic to milk, eggs, wheat, and soy may what
may outgrow their allergy, no way to prevent food allergies
what is contact dermatitis
type IV (delayed) reaction from direct contact with antigen
examples of contact dermatitis
poison ivy, cosmetics(tattoo ink), metals(necklaces, rings)
s/sx of contact dermatitis
inflamed, warm, swollen itchy skin/ blisters may form, drain and become infected
allergic reactions from drug reactions
any drug may cause reaction, any body tissue may be involved, symptoms vary (skin rash, itching, fever, hematologic or hepatic reactions), may occur 7-10 days after initial exposure, resolves after drug discontinued
T or F. allergic rhinitis is caused by type III sensitivity
false; allergic rhinitis is inflammation of nasal mucosa caused by type I hypersensitivity reaction to inhaled allergens
what are antihistamines
relieve symptoms but do not relieve hypersensitivity
antihistamines can help in what ways
help relieve symptoms of allergic rhinitis, anaphylaxis, drug allergies, dermatologic conditions, allergic conjunctivitis (itchy red eyes), blood/ blood transfusion reactions
antihistamine: first generation H1 receptor antagonists example med
diphenhydramine
what does diphenhydramine do (block histamine receptor)
prevent/reduce most physiologic effects that histamine produces at receptor sites, inhibits smooth muscle constriction in blood vessels/respiratory/GI tract, decrease capillary permeability, decrease salivation and tear formation
mechanism of action for first generation H1 receptor antagonists
occupy same receptors as histamine which prevents histamine from reaching target (block histamine receptor)
uses for first generation H1 receptor antagonists
allergic reaction, motion sickness, insomnia, children may experience paradoxical effect(opposite effect, make kids hyper)
adverse effects of first generation H1 receptor antagonists
CNS depression(drowsy), anticholinergic effects(dy mouth, constipation)
contraindications for first generation H1 receptor antagonists
narrow angle glaucoma, BPH
nursing considerations for first generation H1 receptor antagonists
use caution in older adults, may cause confusion, may thicken secretions
patient education for first generation H1 receptor antagonists
take med before exposure to allergen, tolerance to drowsiness in few days, avoid taking with alcohol, avoid accidental OD
antihistamine: second generation H1 receptor antagonists example med
fexofenadine, loratadine, cetirizine
what are second generation H1 receptor antagonist
does not readily enter the brain from the blood(don’t cross blood brain barrier, do not make you drowsy), bind preferentially to peripheral rather than central H1 receptors, replacing first germination H1, have a mild beneficial effect in chronic asthma
mechanism of action for second generation H1 receptor antagonist
occupy same receptors as histamine which prevents histamine form reaching target (blocks histamine receptors)
uses for second generation H1 receptor antagonist
seasonal allergic rhinitis, minor allergies, itching
nursing considerations for second generation H1 receptor antagonist
safer in older adults(because not affected in CNS, non drowsy), use caution in renal failure
patient education for second generation H1 receptor antagonist
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 antihistamine to a patient, the nurse explains that second generation H1 antagonists differ from first generation antagonists by
do not cross the blood brainer barrier/ reducing side effect of sedation (drowsy)
