Drug:
Route: PO IV SC topical
Prior exposure? Reaction before? Had it since?
Most recent rx?
Sx: wheeze, SOB, rash, angioedema, GI, cardiovascular
Rash - desquam, location, itch,
Timing after exposure:
Duration:
Treatment: hospital, epi, antihist, etc
Other exposures: (ie other drugs, herbals, bites)
Cofactors: alcohol, exercise, nsaids, infection, poor sleep

Impression:

ix:
PEN-FAST score
?histamine / tryptase
Skin test - only penicillin, rest not great
if currently in a Type 4 rx, order markers of end organ damage

Mx:
is it true?
avoid? challenge? desensitizie?

Summary:

WIP

Basic classifcation

ADRs are unwanted and undersitable effects despite approipiate rx and dosing. common.

ADRs can be broken down into Type A and B (we are concerned mainly about type B)

• Type A (most ADRs % wise) is dose dependent and predictable - expected side effects based on pharmacologic properties of the drug. Ie. tylenol OD, ACEi and dry cough...

• Type B is either immunologic or non immunologic

  • Usually dose INdepedent and more unpredicatable effects
  • Non-immunologic: Idiosyncratic vs mast cell mediated (pseudoallergy)
    • Link to non-ige mediated reactions (ie. direct mast cell, complement activation, IgG mediated, cytokine release reaction)
    • Can occur on first exposure; skin testing is negative; may have atypical symptoms, and may not be reproducible...
  • Immunologic: ie type I - IV

Framework for ADRS on vs off target immediate vs dealyed gell and coombs

Gel and coombs

This should be listed in a table in the document

Type 1 DHR

mostly <1h ige symptoms reqruies previous exposure or crossr earciity

testing: SPT, IDT

aside: mast cell degeranuatoin non IgE

MRGPRX2 receptors ie opiods quiniolones Completion activation (IV iron, contrast) IgG mediated (ie neuromsucalrbl blockinga gents) cytokine relase reaction ie ritux, paclitaxel

do NOT require prior senziation negative skin testing SOMETIMES (opiods are probably exception) may have atypical symptoms ie think fishbane may not be reporudbile on exposiure as no immunological memory and likely dose dep effects etc

Type II

Antibody mediated usually hemolytic anemias you usually will not see this heme territory mostly

classic edxamples: HIT, drug induced cytropenia usually 1 week after exposure

Type III

Complement mediated reaction and antibody complexes and deposition in organs causing damage Serum sickness and vasculitis are classic examples

IV

SCAR vs non severe quite common, well described

Link to page

The baddie of the world T cell mediated +/- macrophages, eos, or neutrophils DELAYED onset, days to weeks Prominent skin findings are the classic manifestation large variance in clinical severity on presentation

Morbiliform drug reaction, FDE, AGEP, DRESS, SJS/TENS it's a bit of a spectrum

insert timing of onset graph Kahn et al JACI 2022 figure

Common and mild FDE urticaria MB rash

uncommon and severe (SCARS) SJS TEN DRESS AGEP

Approach general

History

• rash, mucosa, systemic involvement
• photos
• TIMING (latency, recent vs remote)
• treatment - severe or mild, anaphylaxis? AH, steroids, hostpial, ED visits...
• use before or after
• any mimickers? CU, viral exanthem, autoimmune condiitons like vascul, pemphigus

For patients who don't remvmer... if it's catatrophic they usually remember..

best to document a drug vs time chart day 0 = rash first appernce

RED FLAGS

• fever (could be isoalted drug fever, serum sickness, vasculitis,dru gionduced lupus, dress sjs ten AGEP)
• SCAR type rashes, blistering, desqumation during ACUTE phase (not healing phase)
• other end organ involvement

what's the risk type of allergy additional testing? recommendations

Drug allergy testing basics

SPT, IDT, patch testing, after 4-6 weeks POST reaction, lower cahnce for false negatives

Immediate reaction history:

• SPT/IDT
• only penicillin (drug major + minor) has good NPV
• other testing has limited evidence...
• there should be published non irritatnt concentreations for skin tests
• IDT must be steriole form so IV psosible or SC possible

drugallergy.ca can be used to find the right concentrations

patch testing

• DRESS AGEP
• extensive drug exathems
• fixed drug eruptions * (patch should be applied WHERE the rash occurs, not just any random space)

when do u do patch testing vs IDT? drug abiliabilty as above patch testing preferred for SCARs IDT if patch testing negative that's the classic approach

BUT now: BOTH are safe for DRESS and IDT is more snseititive than patch

so you've done everything. 3 outcomes

1. avoid. if confirmed drug allergy, type II III or SCAR, or if equilvalent alternativers are available

potenitally need to avoid cross reactive drugs

2. challenge

• only true gold standard
• graded vs single dose ie 10 90%
  • if higher risk then do in hospital, may need IV access, 4 steps maximum (ie 0.1%, 1% 10%, full dose)
• weigh benefit vs risk
• can also avoid and delay challenge for a few years

generally don't challenge for SCAR type 2 or III or recent life threatneing anaphylaxis higher risk ofc with bad heart resp conditiosn etc

3. desensizative if NO other alternative really see link to separate page induction of TEMPORARY state of tolerance starting dose 1/10,000 or less mechanism not fully understood but possible mechs include changes to mast cell surface receptor expression, IgG blocking ab, alterted singnaliing, etc.

allows for drug despite confirmed hyperesneiivity resource intentisve DONT do for SCAR features though

section for other drugs until another page is made:

iron reactions

Mechanisms: IgE (fairly rare), direct mast cell activation, Fishbane reaction (usually consist of acute chest and back tightness and joint pain without severe symptoms, such as hypotension, wheezing, stridor, or laryngeal edema) Testing: no skin tests are reliable in this case. Only an IV challenge is helpful. Management:

1. if direct mast cell => usually try another agent and go very slow
2. if Fishbane, can stop infusion for 15 mins and observe and treat with Tylenol; if improves can run slower

NSAID

generally NSAID induced AAE occurs within 2-3 hours of NSAID ingestion

Ddx is true IgE mediated vs pharmcologic class effect

-Isolated urticaria within 2 hours of NSAID ingestion on repeated exposures is consistent with NSAID induced urticaria which is a cyclo-oxygenase -1 (COX-1) mediated reaction (pharmacologic class effect).
-Consider challenge with celebrex which is a cox-2 selective
-As such, we have advised to continue to avoid all NSAIDs moving forward as at higher doses they may cause repeated urticaria. 
-They can continue to take tylenol without issue. 
-Should he require NSAIDs in the future (beyond topical and low doses which can be administered without issue) he can be re-assessed with a supervised challenge

The patient does not have a history of asthma or nasal polyps
The patient does not have a history of chronic urticaria
Their reaction is most in keeping with COX-1 mediated