N20025: E3: Drugs to Decrease Histamine Effects & Allergic Response
Nursing: Second-generation H1 receptor antagonists
-2nd gen H1 safer for older adults -Caution in renal failure
What are First-generation H1 receptor antagonists used to treat
-Allergic reaction -Motion sickness -Insomnia
Indications for use: Antihistamines
-Allergic rhinitis -Anaphylaxis -Allergic conjunctivitis -Drug allergies, pseudoallergies -Blood/blood product transfusion -Dermatologic conditions
Drug Reactions
-Any drug may cause reaction -Any body tissue may be involved -May occur 7-10 days after initial exposure -Resolves after drug D/C
Type IV Hypersensitivity (Delayed)
-Cell-mediated response -Sensitized T lymphocytes react with antigen to cause inflammation -no antibody looking for antigen = longer response time EXAMPLES -Tuberculin test -Contact dermatitis -Graft rejection
What happens in the allergic response when histamine stimulates its receptors
-Contraction of smooth muscles in respiratory tract (wheezing) -Stimulation of Vagus nerve -Increased permeability of veins & capillaries (edema) -Dilation of capillaries in skin -Increased mucus secretion -Stimulation of peripheral nerve endings -Increase secretion of gastric acid -Increased HR and force
Characteristics of Second-generation H1 receptor antagonists
-Do not readily enter the brain from the blood -Bind preferentially to peripheral rather than central H1 receptors (less CNS effect)
What happens in the allergic response
-Histamine is released in response to stimuli (allergic reactions, cellular injury) -After released, its target cells are in the blood vessels, respiratory & GI tract
What happens to the affected skin in contact dermatitis
-Inflamed, warm, swollen, itchy -Blisters may form, drain, and become infected -Rash in 24 hours after contact
Type III hypersensitivity (Immune Complex)
-Mediated by IgG or IgM -Forms antigen-antibody complexes --> acute inflammatory reaction in tissue EXAMPLE -Serum sickness
Type II hypersensitivity (Cytotoxic)
-Mediated by IgG or IgM -Direct damage to cell surface EXAMPLES -Blood transfusion reactions -HDN, hemolytic anemia -penicillin, heparin reactions
Mild vs severe anaphylaxis
-Mild: itching, rhinitis -Severe: respiratory distress cardiac collapse, life threatening
Sx of allergic rhinitis
-Nasal congestion -Itching, sneezing -Watery drainage -Itching of throat, eyes, ears
Seasonal disease allergic rhinitis
-Response to airborne pollens -Most common in spring/fall -Aka hay fever
Perineal disease allergic rhinitis
-Response to nonseasonal allergens -Dust mites -Molds -Animal dander
What are Second-generation H1 receptor antagonists used to treat
-Seasonal allergic rhinitis -Minor allergies -Itching
Symptoms of drug reactions VARY but may include...
-Skin rash -Itching -Fever -Hematologic or hepatic reactions
Pt Education: Second-generation H1 receptor antagonists
-Take med *before* exposure to allergen -Avoid taking with Alcohol -Avoid accidental OD -Teach proper nasal spray use if needed
Pt education: First-generation H1 receptor antagonists
-Take med *before* exposure to allergen -Tolerance to drowsiness in few days -Avoid taking with Alcohol (CNS -) -Avoid accidental OD
Nursing: First-generation H1 receptor antagonists
-Use caution in older adults (r/t confusion & dizziness) -May thicken secretions
What is the cause of Type I, II, & III hypersensitivity reactions
Antibody molecules
drug-drug interactions of First-generation H1 receptor antagonists
Antidepressants CNS depressants
What is the cause of Type IV Hypersensitivity Reactions
Antigen Specific T Cells
Adverse Effects of First-generation H1 receptor antagonists
CNS depression *drowsiness, sedation Anticholinergic side effects *constipation *retention *dry mouth *blurred vision
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 BBB
D. Do not cross the BBB
Example of First-generation H1 receptor antagonists
Diphenhydramine
Serum Sickness
Excessive antigens combine with antibodies cause tissue damage and immune complexes
T/F Allergic Rhinitis is caused by a type III sensitivity
False, type I
Example of Second-generation H1 receptor antagonists
Fexofenadine loratadine cetirizine
Children may experience paradoxical effect to what drug
First-generation H1 receptor antagonists (they get hyper instead of sleepy)
The first chemical mediator released in the allergic/inflammatory response
Histamine (H1)
What are allergic food reactions
Immune response to ingestion of a protein -i.e. shellfish**, fish, corn, seeds, bananas, egg, milk, soy, peanut, tree nuts *high risk of triggering anaphylaxis
Allergic Rhinitis
Inflammation of nasal mucosa caused by type I reaction to inhaled allergens
Where is histamine (H1) found
Mast cells Basophils
Children may outgrow allergies to...
Milk Eggs Wheat Soy
Contraindications of First-generation H1 receptor antagonists
Narrow angle glaucoma BPH
Action of First-generation H1 receptor antagonists
Occupy same receptors as Histamine which prevents histamine from reaching target
Action of Second-generation H1 receptor antagonists
Occupy same receptors as Histamine which prevents histamine from reaching target
Type I hypersensitivity (Immediate)
Occurs within minutes -IgE induced Mast cell activation (causes histamine release) -Usually after 2nd or later exposure -Anaphylaxis (mild to severe) *antibody for antigen is already inside body
What do First-generation H1 receptor antagonists do
Prevent/reduce most physiologic 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
2 Types of Allergic Rhinitis
Seasonal Perennial
What drug class is replacing first gen H1
Second-generation H1 receptor antagonists
What meds have a mild beneficial effect in chronic asthma
Second-generation H1 receptor antagonists
The 4 types of hypersensitivity reactions are based on...
The producing mechanism
T/F Histamine is the first chemical mediator released during inflammatory response.
True
What is contact dermatitis
Type IV reaction from direct contact with an antigen i.e. poison ivy, cosmetics, metals
What are Hypersensitivity Reactions caused by
abnormal immune reaction (antibodies recognize the antigen/irritant)
Hypersensitivity Reactions involve an exaggerated...
allergic response
No known preventative for...
food allergies
How does breast feeding affect food allergies
prevent food allergies as a child but increase them as a person ages
Antihistamines relieve ________________ but do not relieve/stop/cure __________________
symptoms hypersensitivity
Hypersensitivity Reactions can cause...
tissue damage & serious illness
