A 32-year-old man with newly diagnosed pulmonary tuberculosis is started on standard four-drug therapy (HRZE). After 2 weeks of treatment, he develops acute onset jaundice, dark urine, and right upper quadrant tenderness. Liver function tests show ALT 320 U/L, AST 380 U/L, total bilirubin 4.2 mg/dL, and alkaline phosphatase 95 U/L. Hepatitis A, B, and C serology are negative. What is the most appropriate next step in management?