The delayed-release test drugs are 6-mercaptopurine (at a dose of 40 mg daily) or calcitriol (at a dose of 5 mcg three times a week) versus Purinethol (6-MP at a dose of 1-2 mg/kg body weight daily). Calcitriol is a synthetically manufactured replica of a natural substance in the body that is derived from Vitamin D. There is much medical evidence that shows that lack of Vitamin D can be a possible risk factor in developing autoimmune disorders, including Crohn's Disease. Moreover, calcitriol has been shown in animal models to improve the symptoms of Crohn's Disease.