A 28-year-old woman presents to the emergency department with a 3-day history of fever, malaise, and widespread erythematous macules on her trunk and extremities. On examination, she has oral ulceration, conjunctival injection, and genital erosions. Skin biopsy confirms full-thickness epidermal necrosis. She reports starting trimethoprim-sulfamethoxazole 5 days ago for a urinary tract infection. Her vital signs are stable, and she has <10% body surface area involvement. What is the most appropriate immediate next step in management?