Drugs for IBD

Which mechanism of action is shared by both azathioprine and 6-mercaptopurine in the treatment of inflammatory bowel disease?

A 32-year-old woman from Delhi presents with a 6-month history of bloody diarrhoea, abdominal cramping, and tenesmus. Colonoscopy reveals continuous mucosal inflammation limited to the colon with crypt abscesses on biopsy. She is started on induction therapy. After 4 weeks of standard therapy, her symptoms persist with 6–8 stools daily and faecal calprotectin of 380 μg/g. Which of the following is the most appropriate next step in management?

A 28-year-old man with Crohn's disease involving the terminal ileum presents with 4 weeks of worsening diarrhoea (8–10 stools daily), abdominal pain, and weight loss of 3 kg. He is currently on mesalamine 3 g/day and prednisolone 30 mg/day (started 2 weeks ago). Laboratory investigations show: Hb 9.2 g/dL, albumin 2.8 g/dL, CRP 85 mg/L. He has no fever, no signs of obstruction, and CT enterography shows no abscess. Which of the following is the most appropriate next step in management?