- 6-thioguanine can cause serious liver injury in inflammatory bowel disease patients. Dubinsky, M.C., Vasiliauskas, E.A., Singh, H., Abreu, M.T., Papadakis, K.A., Tran, T., Martin, P., Vierling, J.M., Geller, S.A., Targan, S.R., Poordad, F.F. Gastroenterology (2003)