A 26-year-old man presents with a 2-week history of asymmetric joint pain affecting his right knee and left ankle, lower back stiffness that improves with activity, and tenderness at the Achilles tendon insertion. He also reports intermittent eye redness and a burning sensation on urination. He denied any recent gastrointestinal symptoms but recalls a treated episode of nongonococcal urethritis one month ago. On exam, there is an effusion of the right knee, enthesitis at the left Achilles tendon, and mild conjunctival injection bilaterally. Laboratory studies show HLA-B27 positivity, normal rheumatoid factor, and a negative joint aspiration culture. Which of the following is the most appropriate initial therapy for this patient’s condition?