A 28-year-old woman with a 10-year history of atopic dermatitis presents with widespread erythema, edema, and oozing affecting >50% of her body surface area. She has been using high-potency topical corticosteroids continuously for the past 6 months with only transient improvement. She reports severe sleep disturbance due to pruritus and has missed work multiple times. Baseline investigations show normal renal and hepatic function. What is the most appropriate next step in management?