A 62-year-old man with gout presents to the ED for fever, malaise, and a progressively worsening rash. Eight weeks ago, he started a new medication for gout prophylaxis. Over the last 5 days he developed an erythematous maculopapular (morbilliform) rash that began on the face and upper trunk and is now diffuse. He also notes facial swelling. Exam shows diffuse tender morbilliform eruption with periorbital edema and generalized lymphadenopathy. Labs: WBC 15,800/µL with eosinophils 14%, AST 210 U/L, ALT 240 U/L, creatinine 1.9 mg/dL (baseline 1.0). Which of the following is the most likely diagnosis?