AM Report Pearls: 5 As of Drug Rxns, Allergic Drug Rxns Timing

AM Report Pearls: 5 “A” Classes of Common Drug Reactions – always take a history of these drugs!

  • Allopurinol
  • NS(A)IDs
  • Anti-epileptic Drugs
  • ARVs
  • Sulf(A)

 AM Report Pearls: Types of Allergic Drug Reactions:

We discussed how different drugs have different timelines for when they cause reactions based on their pathophysiology. This nifty table of allergic drug reactions shows timeline, pathophys & examples!

Type Onset Pathophysiology Examples
Type I Immediate (minutes) Mediated by IgE & mast cells Urticaria within minutes to PCNs, periperative anaphylaxis to neuromuscular blockade, infusion rxns to chemo
Type II Delayed (usually 5-8 days after) Antibody-mediated cell destruction (uncommon) Drug-induced hemolytic anemia (esp to cephalosporins, NSAIDs and quinine), drug-induced thrombocytopenia (esp to heparin), drug-induced agranulocytosis (to PTU, flecainide)
Type III Delayed (at least a week) IgG:drug immune complex deposition & complement activation Drug-induced hypersensitivity vasculitis (PCN, Cephalosporin, sulfonamides, phenytoin, allopurinol)
Type IV Delayed (sometimes days to weeks later) T-cell mediated Maculopapular/morbilliform eruptions, AGEP, SJS/TEN, DRESS (aka drug-induced hypersensitivity syndrome), drug fevers

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