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41 terms

Pharmacotherapy: Allergic and Pseudoallergic Drug Reactions

What antibody is involved in a type I allergic reaction?
IgE binds to these 2 cells
1) Mast Cells
2) Basophils
What happens when the antigen binds the IgE bound to these cells
Causes cells to release cytokines
What are 2 symptoms of a type I allergic reactions
1) Anaphylaxis
2) Urticaria
What are 4 antibiotics that most commonly cause type I allergic reactions
1) Penicillins <<< MAIN ONE
2) Cephalosporin
3) Sulfonamides
4) Vancomycin
What else that isn't an antibiotic most often causes type I allergic reaction
What cephalosporins are most cross reactive with penicillins
1st Generation
Type II allergic reactions involves what antibody
What type of reaction occurs
IgG binds to target hapten or antigen and causes complement destruction of target cells
2 Types of reactions that occur
1) Hemolytic Anemia
2) Thrombocytopenia
4 Drugs that most commonly cause type II allergic reactions
1) Heparin
2) Quinidine
3) Methyldopa
4) Penicillins
Type III allergic reactions involve which 2 antibodies
1) IgG
2) IgM
What happens?
The antibodies bind the antigen or hapten and then form complexes which get deposited in vessel walls and activate complement resulting in vasculitis (excess of antibody and little antigen)
How long does it normally take for type III symptoms to slow
1-2 weeks
What 3 things occur
1) Serum Sickness
2) Vasculitis
3) Lupus
4 Agents that cause type III allergic reactions
1) Penicillins
2) Sulfonamides
3) Radiocontrast Agents
4) Phenytoin
How can we prevent this with radiocontrast agents
Premedicate with prednisone or benadryl
What is involved in a type IV reaction
NO ANTIBODIES, only T cells
Type IV is aka a
Delayed Reaction
What is an immediate hypersensitivity reaction
Type I
Type IV reaction symptoms
Itchty flakey skin reactions / contact dermatitis
What are 3 things that cause these
1) B-Lactams
2) Sulfonamides
3) Phenytoin
Pseudoallergic Reactions do not involve
What is an allergic reaction involving the skin that is very serious? What does it progress to1
SJS progresses to TEN
A patient experiencing anaphylaxis should be observed for at least
12 hours
Treatment of anaphylaxis
1) Epinephrine IM or SQ q 5 minutes / NS infusion
2) If not responding then epinephrine infusion
3) +/- diphenhydramine ; Ranitidine ; Inhaled B-agonist ; dopamine (hypotension refractory to NS and epinephrine) ; hydrocortisone
What is percutaneous (prick) skin testing
They put a drop on the skin and take a needle through the drop and measure allergic response
What is intradermal skin testing
Actually inject antigen into the skin
Cephalosporin / Penicillin Cross Sensitivity
~4% or less ; more common cross-reactivity with 1st generation cephalosporins
Describe carbapenems
ARE CROSS REACTIVE with penicillins
Describe monobactams
Not corss reactive with any beta lactam except ceftazidime
What 2 agents most commonly cause SJS and TEN
1) Sulfonamides
2) Anticonvulsants
What is the main reaction we see with aspirin?
AERD (aspirin-exacerbated respiratory disease)
ASA / NSAIDs can also cause? How often do ASA / NSAIDs cause anaphylaxis
1) Urticaria (most common IgE reaction)
2) Second only to beta-lactams
Opiate reactions are
Pseudoallergic reactions
These agents cause histamine release
How can we help patients on opidates
Pretreat with antihistamines
What chemotherapy agents cause allergic reactions?
Any of them
One of the only agents that doesn't need to form a complex to cause allergic reaction
What can cause a pseudoallergic reaction if the infusion rate is too high
You do not attempt desensitization if the patient
Had anaphylaxis to the agnet (anaphylaxis is a contraindication to desensitization)