Q. A 35-year-old male patient presents to the clinic with a three-month history of a gradually enlarging, painless skin ulcer on his right forearm. He recalls an insect bite at that location during a recent hiking trip in South America. He has also reported low-grade fevers and malaise over the past few weeks. His past medical history is unremarkable, and he takes no medications. On examination, the ulcer measures approximately 3 cm in diameter, with raised, indurated edges and a granulating base. There are no regional lymphadenopathies. However, physical examination is significant for splenomegaly. Blood tests show that Hemoglobin is 12.5 g/dL, White blood cell count is 4000/µL, and Platelet count is 80,000/µL. Bone marrow biopsy reveals numerous macrophages laden with amastigotes. What is the most appropriate next step in the management of this patient?