A 16-year-old boy is brought to clinic for acne. He has numerous inflammatory papules and pustules on the face and upper back. He has been adherent to an over-the-counter regimen that includes a topical retinoid at night and benzoyl peroxide in the morning for the past 10 weeks, with only minimal improvement. He has no systemic symptoms. Physical examination shows multiple erythematous papules and pustules, a few closed comedones, and no nodules or cysts. Which of the following is the most appropriate next step in management?

(Assume no medication allergies and that the patient is not taking other medications.)