Exanthematous Drug Eruptions

A 50-year-old woman with bipolar depression presents with a widespread pruritic rash of 1 day's duration. She is afebrile and otherwise well. She has a history of childhood eczema and is allergic to sulfonamide antibiotics. Her medications include thyroxine daily, naproxen intermittently, and lamotrigine, which she began taking 3 weeks earlier. How should this case be evaluated and treated?