18th March 2024

Gell and Coombs classification of drug reactions

In the context of drug reactions:

Type I: Drug-induced anaphylaxis is one of the most common causes of anaphylaxis, especially in inpatients and in older populations. Furthermore, when anaphylaxis is secondary to drugs it is associated with a worse prognosis. It can be related to any drug, however non-steroidal anti-inflammatory drugs (NSAIDs) and antibiotics (penicillins) are the most common culprits.

Type II: Reactions include heparin induced hypersensitivity. This occurs due to activation of IgG antibodies against heparin-platelet factor 4 complexes.

Type III: A Streptococcal throat infection leading to immune complex deposition in the kidney causing glomerulonephritis usually within 10 to 21 days.

Type IV: Examples of drug-induced delayed hypersensitivity reactions mediated by T cells include: DILI (drug-induced liver injury), DRESS (drug reaction with eosinophilia and systemic symptoms), TEN (toxic epidermal necrolysis), DIA (drug-induced agranulocytosis) and AGEP (acute generalised exanthematous pustulosis).