Which drug class is responsible for the majority of SJS/TEN cases in developed countries, and what is the approximate attributable risk?

Explanation

## Drug-Induced SJS/TEN: Epidemiology and Risk **Key Point:** Antibiotics—particularly sulfonamides and beta-lactams—are the leading drug class implicated in SJS/TEN in developed countries, accounting for approximately 30–40% of all drug-induced cases. ### Most Common Culprit Drugs | Drug Class | Examples | Relative Risk | % of Cases | |------------|----------|---------------|------------| | **Antibiotics** | Sulfonamides (TMP-SMX), amoxicillin, cephalosporins | Very high | 30–40% | | Anticonvulsants | Phenytoin, carbamazepine, lamotrigine, phenobarbital | High | 15–25% | | NSAIDs | Ibuprofen, naproxen, oxicams | Moderate | 10–15% | | Antiretrovirals | Nevirapine, abacavir | High (in HIV+ patients) | 5–10% (overall) | | Allopurinol | — | High | 5–8% | **High-Yield:** In developing countries (including India), anticonvulsants and allopurinol are proportionally more common causes due to different prescribing patterns and genetic predisposition (HLA-B*1502 for carbamazepine in Asian populations). **Mnemonic:** **SCAN** — **S**ulfonamides, **C**arbamazepine, **A**llopurinol, **N**evirapine (the "big four" high-risk drugs). **Clinical Pearl:** The risk is dose-independent and idiosyncratic, not dose-related. Even a single dose can trigger SJS/TEN in susceptible individuals. Genetic factors (HLA polymorphisms) play a major role in susceptibility.