Q. A 42-year-old woman with a known history of HIV infection presents to the outpatient department for routine follow-up. She has been feeling well and is currently on antiretroviral therapy. She is not currently on any prophylactic medications. On physical examination, she is vitally stable, and the rest of her systemic examination is unremarkable. She also has no respiratory symptoms. On lab investigations, his medical record indicates that his last CD4 count, taken three months ago, was 195 cells/µL. A repeat CD4 count obtained today shows a decrease to 165 cells/µL. What is the most appropriate prophylactic medication to prescribe for this patient?