Evaluation of tolerance to mercaptopurine in patients with inflammatory bowel disease and gastrointestinal intolerance to azathioprine Guillermo Bastida; Diego Alvarez-Sotomayor; Mariam Aguas; Marisa Iborra; Javier Del Hoyo; Sergio Béjar-Serrano; Alejandro Garrido-Marín; Elena Valero-Pérez; Pilar Nos;