Carbamazepine is most commonly associated with which idiosyncratic reaction?

• A. Malignant hyperthermia
• B. Drug-induced liver injury
• C. Allergic reactions/hypersensitivity
• D. Toxic epidermal necrolysis (SJS)

Answer: (D)

The concept being tested is that carbamazepine can trigger a severe, idiosyncratic immune-mediated adverse reaction, most famously a cutaneous reaction on the Stevens-Johnson/TEN spectrum. These reactions are not dose-related and typically appear within the first weeks of therapy. They begin with fever and flu-like symptoms, then progress to mucosal involvement and a widespread, often rapidly spreading rash with epidermal detachment. The underlying mechanism is an immune response where drug-specific T cells target keratinocytes, leading to extensive cell death; genetic factors (such as certain HLA variants in specific populations) can markedly increase risk. Because of the potential for rapid progression and high mortality, Stevens-Johnson syndrome and toxic epidermal necrolysis are the classic idiosyncratic reactions associated with carbamazepine.

Malignant hyperthermia is not linked to carbamazepine and relates to anesthetic exposure in susceptible individuals. Drug-induced liver injury can occur with many drugs but is not the hallmark idiosyncratic adverse reaction that carbamazepine is best known for. Allergic/hypersensitivity reactions can occur, but the most characteristic and severe idiosyncratic reaction for this drug is SJS/TEN.