chapter 32, drug therapy to decrease histamine effects + allergies PHARM

what is the allergic response

- Histamine is the 1st chemical mediator released

- found in mast cells and basophils, which are looks for allergens

- released in response to stimuli (ex. allergic reactions)

what happens when histamine stimulates its receptors

- contractions of smooth muscles in respiratory tract

- stimulation of vagus nerve

- increased permeability of veins and capillaries

- stimulation of peripheral nerve endings

- dilation of capillaries in the skin

-increased heart rate and force

in general, what is a hypersensitivity reaction

- involves and exaggerated allergic response

- can cause tissue damage and serious illness

- caused by an abnormal immune reaction

what is type 1 hypersensitivity

- immediate hypersensitivity

- aka anaphylactic response

- occurs within minutes

- usually after 2nd or later exposure

- mild: itching, rhinitis

- severe; anaphylaxis-respiratory distress, cardiac collapse, life threatening

what is type 2 hypersensitivity

- Cytotoxic: toxic to cells

- generates direct damage to cell surface

-blood transfusion reactions

- ex; hemolytic disease of newborns or hemolytic anemia

what is type 3 hypersensitivity

-immune complex

- serum sickness

what is type 4 hypersensitivity

- delayed hypersensitivity

- needs a couple days for body to cause a reaction

- tuberculin test

- contact dermatitis

- graft rejection

what is allergic rhinitis

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

what are the symptoms of of allergic rhinitis

-nasal congestion

- itching, sneezing

- watery drainage

- itching of throat, eyes, ears

allergic rhinitis: what is seasonal disease

- aka hay fever

- response to airborne pollens

- inahled allergens

allergic rhinitis: what is perennial disease

- response to nonseasonal allergens

- dust mites

- animal dander

- inhaled allergens

what is an allergic food reaction

-immune response to ingestion of a protein (ex. shellfish, peanut)

- higher risk of triggering anaphylaxis

- children may outgrow their allergy

- no known preventative

what is contact dermatitis

- type 4 hypersensitivity reaction from direct contact with antigen

- ex: poison ivy, cosmetics, metals

- affected skin is: warm, swollen, itchy

- blisters may form, drain, and become infected

what is a drug allergic reaction

- any drug may cause reaction

- anybody tissue may be involved

-may occur 7-10 days after initial exposure

- usually resolves after drug is stopped

what is an antihistamine

- relieve symptoms but does not relieve hypersensitivity

- used for all types of allergic reactions

which drug is a first generation H1 receptor antagonist

diphenhydramine

action of diphenhydramine

- occupy same receptors as histamine which prevents histamine from reaching target

use of diphenhydramine

- allergic reaction

-insomnia

- children may experience paradoxical effects (cause hyperness instead of sleepy)

adverse effects of diphenhydramine

-CNS depression

-Anti cholinergic effects

Contraindications for Diphenhydramine

- narrow angle glaucoma

- BPH

what is the nursing considerations for diphenhydramine

- caution in older adults; may cause confusion

- may thicken secretions

patient education for diphenhydramine

- take med before exposure to allergen

- tolerance to drowsiness in a few days

- avoid taking with alcohol

- avoid accidental overdose

which drugs are second generation H1 receptor antagonists

-fexofenadine

-loratadine

-cetirizine

true or false; second generation H1 receptor antagonists pass the blood brain barrier

false

second generation H1 receptor antagonists also do what

have a mild beneficial effect in chronic asthma

what is the action for second generation H1 receptor antagonists

occupy the same receptors as histamine which prevents histamine from reaching target

use of second generation H1 receptor antagonists

-Seasonal allergic rhinitis

-Minor allergies

-Itching

Nursing considerations for second generation H1 receptor antagonists

- safer in older adults

- caution for pts with renal failure

patient education for second generation H1 receptor antagonists

-take med before exposure to allergen

- teach proper use of nasal spray if needed

-aviod taking with alcohol

-aviod accidental overdose