A 4-year-old boy with known G6PD deficiency is brought to the pediatrician by his mother with a blistering pruritic rash. On examination, numerous tense vesicles and bullae are seen on his neck, lower abdomen, and extremities. Ulcerative lesions on his buccal mucosa are also noted. Direct immunofluorescence of a skin biopsy later reveals linear deposits of immunoglobulin A (IgA) at the dermoepidermal junction. Which of the following treatments is recommended for this patient?