Rectal foam or suppositories to treat ulcerative colitis (proctitis) or for Crohn's disease affecting the rectum. The letters α and β[18] denote absolute stereochemistry at chiral centers—a specific nomenclature distinct from the R/S convention[19] of organic chemistry to denote absolute configuration of functional groups, known birli Cahn–Ingold–Prelog priority rules. The http://ezproxy.cityu.edu.hk/login?url=https://tr.wikipedia.org/wiki/Vitamin