Antimicrobials USMLE Step 1 Practice Question

A 39-year-old woman with newly diagnosed tuberculosis begins standard four-drug therapy including rifampin. Within days, she notices orange discoloration of her urine and contact lenses. Three weeks later, her seizure frequency increases despite adequate phenytoin dosing. Laboratory studies show elevated liver enzymes (AST 85 U/L) and sputum acid-fast bacilli staining remains positive. She denies fever, rash, or jaundice. Which antimycobacterial agent most likely explains her clinical findings?