Zelmac is used to treat irritable bowel syndrome. Relieve associated symptoms such as constipation. Zelmac is used to treat severe constipation in the elderly and adolescents. Zelmac tablets are used to treat irritable bowel syndrome and relieve its symptoms. Zelmac is considered one of the medications that have proven effective in treating severe irritable bowel syndrome, which is accompanied by bloating, constipation and gas. Relieve symptoms associated with irritable bowel syndrome.