Drug Therapy to Decrease Histamine Effects and Allergic Response

histamine

1st chemical mediator released in immune & inflammatory response

mast cells and basophils

histamine is found in _______ and _______

histamine

this is released in response to stimuli (allergic reactions, cellular injury) and attaching to target cells in the blood vessels, respiratory tract, and GI tract

• contraction of smooth muscles ini respiratory tract

• stimulation of vagus nerve

• increased permeability of veins and capillaries

• increased secretions from mucus glands

• stimulation of peripheral nerve endings

• dilation of capillaries in skin

• increase secretion of gastric acid

• increased heart rate and force

when histamine stimulates it receptors…what happens? (8)

hypersensitivity reactions

involves an exaggerated allergic response; can cause tissue damage & serious illness, caused by an abnormal immune reaction

antibody molecules

Types 1, 2, and 3 involve…

antigen-specific T cells

type 4 involves…

hypersensitivity reactions

there are 4 types of…

Type 1

type of hypersensitivity that occurs within minutes; involves IgE mast cell activation and typically occurs after 2nd or later exposure; can be mild to severe

itching, rhinitis

symptoms of mild type 1 reaction

anaphylaxis (respiratory distress & cardiac collapse)

severe type 1 response

cytotoxic

another name for type 2 reaction

Type 2

reaction mediated by IgG or IgM that generates direct damage to cell surface

blood transfusion reactions, hemolytic disease of the newborn, hemolytic anemia

what are 3 examples of things that are caused by Type 2 reaction

penicillin and heparin

type 2 hypersensitivity can also be in reaction to medications such as _____ and _____

immune complex reaction

type 3 reaction is also known as…

Type 3

mediated by IgG or IgM and forms antigen-antibody complexes, acute inflammatory reaction in tissue; serum sickness

Type 3

this reaction is typically after antibody transfusion or reaction to some meds

delayed hypersensitivity

type 4 reaction is also known as…

Type 4

a cell mediated response where sensitized T lymphocytes react with an antigen to cause inflammation

tuberculin test, contact dermatitis, and graft rejection

what are 3 examples of type 4 hypersensitivity?

True

True or False: histamine is the first chemical mediator released during the inflammatory response

True

True or False: Four classifications of hypersensitivity reactions exist

allergic rhinitis

inflammation of nasal mucosa caused by type 1 reaction to inhaled allergens

nasal congestion, itching, sneezing, watery drainage, itching of throat/eyes/ears

symptoms of allergic rhinitis (5)

seasonal disease

response to airborne pollens

perennial disease

response to nonseasonal allergens such as dust mites, molds, and animal dander

allergic food reactions

immune response to ingestion of a protein

shellfish

most common food allergy in adults

shellfish, fish, corn, seeds, bananas, eggs, milk, soy, peanuts, tree nuts

what are some common food allergies? (10)

allergic food reactions

these have a higher risk of triggering anaphylaxis

milk, eggs, wheat, soy

common childhood food allergies (4)

False

True or False: we can prevent food allergies

contact dermatitis

type IV reaction from direct contact with antigen (ex. poison ivy, cosmetics, metals)

inflamed, warm, swollen, itchy, blisters

what happens to affected skin with contact dermatitis? (5)

24 hrs

it typically takes about ___ for contact dermatitis rash to form

skin rash, itching, fever, hematologic or hepatic reactions

common symptoms of drug allergies (5)

7-10 days

drug allergic reactions can occur ____ after initial exposure

False

True or False: allergic rhinitis is caused by type 3 sensitivity

antihistamines

medication that relieves symptoms of allergen but do not cure the allergy

allergic rhinitis, anaphylaxis, allergic conjuctivitis, drug allergies, pseudoallergies, blood/blood product transfusion, dermatologic conditions

what are some indications for antihistamines (7)

diphenhydramine

example of a first generation H1 receptor antagonist

first generation H1 receptor antagonists

this drug class prevents/reduces most physiologic effects that histamine produces at receptor sites (blocks histamine)

• inhibits smooth muscle constriction in BV, respiratory, GI tract

• decrease capillary permeability

• decrease salivation and tear formation

first generation H1 receptor antagonists (diphenhydramine)

this drug class (drug example)’s action is to occupy the same receptors as Histamine which prevents histamine from reaching target

allergic reaction, motion sickness, insomnia, possible paradoxical effects in children

uses for diphenhydramine (4)

CNS depression, anti cholinergic effects (dry mouth, urinary retention, constipation)

adverse effects of diphenhydramine (2)

narrow angle glaucoma, BPH

contraindications of diphenhydramine (2)

use caution in older adults, may cause confusion, dizziness, fall; may thicken secretions

nursing considerations for diphenhydramine (2)

take med before exposure to allergen, tolerance to drowsiness in few days possible, avoid taking with ETOH, avoid accidental OD

patient education for diphenhydramine (4)

fexofenadine, loratadine, cetirizine

3 examples of second generation H1 receptor antagonists

allegra

trade for fexofenadine

claritin

trade for loratadine

zertec

trade for cetirizine

second gen H1 receptor antagonists

antihistamine that doesn’t readily enter the brain from the blood, binds preferentially to peripheral rather than central H1 receptors, replaces first gen, has mild benefits in chronic asthma

second gen H1 receptor antagonists

action of this drug class is to occupy same receptors as histamine to prevent histamine from reaching target (2nd type)

seasonal allergic rhinitis, minor allergies, itching

uses of second gen H1 receptor antagonists (3)

safer in older adults, use caution in renal failure (b/c can lead to toxicity)

nursing considerations for second gen H1 receptor antagonists (2)

take med before exposure to allergen, teach proper use of nasal spray, avoid taking with ETOL, avoid accidental OD

patient education for second gen H1 receptor antagonists (4)

D

When explaining the options for anti-histamines to a patient, the nurse explains that second generation H1 antagonists differ from first generation H1 antagonists by:

A. cause greater CNS sedation
B. are available by prescription only
C. are more cost effective
D. do not cross the blood brain barrier