A 58-year-old man with poorly controlled diabetes mellitus (HbA1c 10.2%) presents with a 3-week history of progressive dysphagia and retrosternal chest pain. Endoscopy reveals white plaques in the oesophagus that do not scrape off easily. KOH mount of the biopsy specimen shows pseudohyphae and budding yeast. He is started on fluconazole 200 mg daily. After 5 days of therapy, he develops severe hepatotoxicity with ALT 1200 U/L and bilirubin 4.2 mg/dL. What is the most appropriate next step in management?