Unit 3 - Hypersensitivity Reactions 2 Flashcards
What is the function of corticosteroids?
Anti-inflammatory medicines used to treat a range of conditions
- asthma and chronic obstructive pulmonary disease (COPD)
- hay fever
- hives and eczema
Give an example of a corticosteroid that is used to treat asthma, hay fever and hives and eczema
Prednisone
- tablet
- inhaler
What is anaphylaxis?
Systemic response to hypersensitivity
When does anaphylaxis occur most frequently?
In the 4th decade of life
- particularly when the drug is given parentally
What happens when the body goes into anaphylactic shock?
- blood pressure suddenly drops
- airways narrow - blocking normal breathing
What are the symptoms of anaphylactic shock?
Skin reactions - hives - flushed skin - paleness Suddenly feeling too warm Feeling like you have a lump in your throat or difficulty swallowing Nausea, vomiting or diarrhoea Abdominal pain A weak and rapid pulse Runny nose and sneezing Swollen tongue and lips Wheezing or difficulty breathing Sense that something is wrong with your body Tingling hands, feet, mouth or scalp Struggling to breathe Dizziness Confusion Sudden feeling of weakness Loss of consciousness
What are the three main types of adrenaline autoinjector?
EpiPen
Jext
Emerade
What is hyposensitisation?
To inject repeatedly small quantities of allergen
Results in an increase in IgG against allergen
- corresponding fall in specific IgE against allergen
What allergens can be used for hyposensitisation?
Pollinex - grass pollen
Pharmalgen - bee and wasp venom
Which group of patients are not eligible for hyposensitisation treatment to grass pollen?
Asthmatic patients
- more likely to have a severe reaction
Why are asthmatics included in hyposensitivity treatment for wasp and bee venom?
The sting is potentially life threatening, whereas hyposensitisation is under controlled conditions and resuscitation facilities are available
Why should care be taken in hyposensitivity patients taking beta-adrenergic blocking agents (beta blockers) or angiotensin-converting enzyme (ACE) inhibitors?
Medication may mask early signs and symptoms of anaphylaxis and may make the treatment of anaphylaxis more difficult
- beta blockers amplify the adrenaline reaction
- ACE inhibitors - risk of severe anaphylactoid reactions
- angioedema occurs in 0.1% to 0.2% of patients (accumulation of bradykinin)
Which is clinically the most important drug allergy?
Penicillin allergy
- greater than 1% of all adverse reactions still associated with Penicillins
What is the most common cause of anaphylaxis?
Penicillin allergy is the most common cause of fatal and non-fatal anaphylactic reactions.
Several studies suggest that up to 75% of fatal anaphylactic episodes are due to penicillin.
What percentage of people have an allergic reaction after administration of penicillin?
About 0.2% of people treated with penicillin have a reaction upon 1st administration.
About 2% of those treated with penicillin will have a reaction upon 2nd administration
What are the potential hypersensitivity reactions to penicillin?
Hypersensitivity reactions to penicillin:
Rash, diarrhea, nausea,urticaria - more common
Fever, erythema, dermatitis, angioedema, - infrequent
Erythemais redness of the skin or mucous membranes, caused by hyperemia (increased blood flow) in superficial capillaries. It occurs with any skin injury, infection, or inflammation.
Dermatitisusually involves itchy, dry skin or a rash on swollen, reddened skin. Or it may cause the skin to blister, ooze, crust or flake off.
Angioedemais the rapid edema, or swelling, of the area beneath the skin or mucosa. It is normally an allergic reaction, but it can also be hereditary. The swelling happens because fluid accumulates.
0.01% of those treated experience serious adverse event – anaphylaxis.
Mostly occurring with parenteral administration. About 1 in 10 of these will die.
Skin - generalized hives, itchiness, flushing.
Swelling of the lips, tongue or throat.
Respiratory - shortness of breath, wheezes, low oxygen.
Heart & vascular - coronary artery spasm subsequent myocardial infarction or dysrhythmia.
Drop in blood pressure loss of consciousness, shock
WHat other antibiotic has a higher risk of adverse reaction if the patient has a penicillin allergy
An approximate 2–fold greater chance of suffering an allergic reaction to cephalosporin antibiotics if one has a penicillin allergy.
What are the different types of hypersensitivity reactions?
Type I: Immediate Hypersensitivity These allergic reactions (including anaphylactic reaction) are systemic or localized, as in allergic dermatitis (e.g., hives, wheal and erythema reactions) or allergic rhinitis (hay fever) - (Antibody-dependent: IgE)
Type II: Cytotoxic Reaction (Antibody-dependent: IgM, IgG) - Autoimmune
Type III: Immune Complex Reaction (Antibody-dependent: IgM, IgG)
Type IV: Cell-Mediated: Delayed Hypersensitivity (Cell-dependent)
