ID Hypersensitivity Flashcards
Differentiate between type A and type B ADR.
Which type is hypersensitivity in?
Predictable/non-predicatable
dose related/non-related
mortality/morbidity
Type A
- predicatable
- dose-dependant
- significant morbidity
Type B
- unpredictable
- non-dose dependant
- mortality
- HYPERSENSITIVITY
Explain how type II hypersensitivity reactions work. When does it develop?
IgG Mediated Reaction
1. Antigen + IgG antibody attach to target cell –> cause cytotoxicity –> destroys target cell
Within 72 hours of drug exposure
What are symptoms (rare) of type II reactions? (3) What does it indicate happening in the body? what ABX?
- Neutropenia: low neutrophils –> infection
- rare with ABX - Thrombocytopenia: low platelets –> petechial bleeding
- caused by vancomycin - Hemolytic anemia: RBCs destroyed –> dyspnea, fatigue, jaundice
- caused by cephalosporins
Explain type III reactions. How long does it take to develop?
Immune Complex-mediated Reaction
1. Drug binds IGg antibodies –> forms immune complexes
2. Immune complexes activate complement–> attracts neutrophils to the site –> complement precipitates form in blood vessels, joints, glomeruli
uncommon: take 2-3 weeks to develop
What are the symptoms of type III reactions? (2) What is the cause of it?
- Serum sickness: deposit in glomeruli
- FEVER, rash, arthralgia - Vasculitis: deposit in blood vessels
- rash, petechiae, urticaria rash (24hr, show up and fade then show up a different spot)
Explain type IV: cell-mediated reaction 1. How long does it take to develop?
T cells become exposed to drug antigen –> sensitized –> activate macrophages –> activate cytotoxic T cells
Takes 48-72 hours, can take weeks
- DELAYED due to T-cell activation
What are symptoms associated with Type IV- 1 reaction
Cutaneous symptoms
- maculopapular rash (COMMON)
NO FEVER
Explain the complications from a Type IV- 2 cell-mediated reaction (3) Which antibiotic causes each complication?
- DRESS (drug reaction eosinophilia and systemic symptoms)
- High fever, multisystem organ failure
eg. caused by vancomycin - Stevens-johnson syndrome and Toxic epidermal necrolysis (SJS/TEN)
- life threatening
- fever and mucotaneous lesions - Acute generalized exanthematous pustulosis (AGEP)
- superficial pustules and fever
eg. amoxicillin, clindamycin, fluoroquinolone
Is a patient who experiences delayed maculopapular rash at greater risk of developing DRESS or SJS/ TEN with re‐exposure?
No
Explain the mechanism of Type 1 reactions. When does it occur?
Type 1: IgE-mediated reaction (immediate)
1. Allergin binds to IgE antibodies –> binds to mast cell –> degranulation of mast cell –> symptoms caused
2. Requires sensitization (formation of drug-specific IgE antibodies from re-exposure of drug)
Oral: within minutes up to 6 hours
What are symptoms of Type 1 IgE mediated reactions?
- Uticaria
- Pruritus (itch)
- Angioedema (swollen lips)
- Anaphylaxis
NO FEVER
What are characteristics of urticarial rash
- hives
- “wheal and flare”
- “white on a red base”
- itchy
- fade without scarring in 24hrs
- may reappear somewhere else
How long does it take to resolve IgE mediated reaction?
- After discontinuing drug it resolves 3-5 days
What are the 3 possible scenarios for diagnosis of anaphylaxis?
- Sudden onset of illness involvement
a. Skin, hives, itch, swollen lips
AND
b. respiratory symptoms (shortness of breath, wheeze) OR sudden reduced BP or organ failure - 2 or more of the following:
- sudden skin or mucosal symptoms
- sudden respiratory symptoms
- Sudden reduced BP or end organ dysfunction
- Sudden GI symptoms (cramp, vomitting) - Patient with known IgE allergy to drug
- experiences reduced BP after taking drug
(BP less than 90 mm Hg or greater than 30% decrease)
How to treat these symptoms:
maculopapular rash
Uticarial rash
Anaphylaxis
maculopapular rash:
- d/c drug OR symptom management
Urticarial rash
- MUST d/c drug
- symptom management optional
Anaphylaxis
- urgently d/c drug
- call 911
- administer IM epinephrine
