PHARM TEST 3 - DRUG THERAPY TO DECREASE HISTAMINE EFFECTS AND ALLERGIES

The Allergic Response

Histamine

1st Chemical mediator released

Found in mast cells and basophils

Released in response to stimuli (allergic reactions, cellular injury)

After its release, it targets blood vessels, respiratory and GI

Allergic Response

Contraction of smooth muscles in respiratory tract

Stimulates vagus nerve (bronchoconstriction)

Increased permeability of veins and capillaries

Increased secretion from mucus glands

stimulation of peripheral nerve endings

dilation of capillaries in skin

Increase secretion of gastric acid

increased HR and force

Hypersensitive Reactions

Involve an exaggerated allergic response

Can cause tissue damage and serious illness

caused by an abnormal immune reaction

Four types of hyper sensitive reactions

Type 1,2,3 : Antibody molecules

Type IV : Antigen-Specific T Cells

Type 1 Hypersensitivity (Immediate)

Occurs within minutes

IgE induced Mast cell activation

Usually after 2nd or later response

Mild (itching, Rhinitis)

Severe (Anaphylaxis-respiratory distress cardiac collapse, life threatening)

Type 2 Hypersensitivity

Cytotoxic

Mediated by IgG or IgM

Generates direct damage to cell surface

Blood transfusion reactions

Hemolytic disease of newborns, hemolytic anemia

Type 3 Hypersensitivity

Type II or immune complex

Mediated by IgG or IgM

Forms antigen-antibody complexes acute inflammatory reaction in tissue

Serum sickness

Type IV hypersensitivity (Delayed)

Cell mediated response

Sensitized T lymphocytes react with antigen to cause inflammation

TB Test, Contact dermatitis, graft rejection

Allergic Rhinitis

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

Allergic Rhinitis Symptoms

Nasal congestion

Itching sneezing

Watery Drainage

Itchy throat, eyes, ears common

Seasonal disease (hay fever)

Response to airborne pollens

Perennial disease

Response to nonseasonal allergens

Dust, mites, pollens

Animal dander

Allergic Food reactions

Immune response to ingestion of a protein

(shellfish, fish, corn, seeds, bananas, egg, milk, soy, peanut, tree nut)

High risk of trigger Anaphylaxis

Children allergic to milk eggs wheat soy

May outgrow allergies

no known prevention

Contact dermatitis

Type IV reaction from direct contact with antigen (poison ivy, cosmetics, metals)

Contact dermatitis affected skin

Inflamed warm swollen itchy

Blisters may form, drain, and become infected

Drug allergic reactions

Any drug may cause reaction

any body tissue may be involved

symptoms may vary but include

Skin rash, itching, fever, hematologic or hepatic reactions

May occur 7-10 days after initial exposure

Resolves after drug DC

Antihistamines

Relieve symptoms but do not relieve hypersensitivity

Allergic rhinitis

Allergic conjunctivitis

Drug allergies, pseudo allergies

Blood / blood product transfusion

Dermatologic conditions

First generation H1 Receptor antagonists example

Diphenhydramine (Benadryl)

First generation H1 Receptor antagonists action

prevent / reduce most physiological effects that histamine produces at receptor sites

inhibit smooth muscle constriction in blood vessels, respiratory, GI tract

Decrease capillary permeability

Decrease salivation and tear formation

First generation H1 Receptor antagonists use

Allergic reactions

Motion Sickness

Insomnia

First generation H1 Receptor antagonists adverse effects

CNS depression

Anticholinergic effects

Children may experience paradoxical effects

First generation H1 Receptor antagonists contraindications

Narrow angle glaucoma

BPH

First generation H1 Receptor antagonists nursing considerations

Use in caution in older adults, may cause confusion

May thicken secretions

First generation H1 Receptor antagonists PT education

Take med before exposure to allergy

Tolerance to drowsiness in a few days

Avoid taking with alcohol

Avoid accidental OD

Second Generation H1 receptor antagonists examples

Fexofenadine, Loratadine, Cetirizine

Second Generation H1 receptor antagonists

Dose does not enter brain from the blood

bind preferentially to peripheral rather than central H1 receptors

replacing first generation H1

Have a mild beneficial effect in chronic asthma

Second Generation H1 receptor antagonists Action

Occupy same receptors as histamine which prevents histamine from reaching target

Second Generation H1 receptor antagonists use

Seasonal allergic rhinitis

Minor allergies

itching

Second Generation H1 receptor antagonists nursing considerations

Safer in older adults

Use caution in renal failure

Second Generation H1 receptor antagonists PT education

Take med before exposure to allergen

Teach proper sue of nasal spray if needed

Avoid taking with alcohol

Avoid accidental OD