A system whereby a substance which is orally taken and to be delivered into the lower digestive tract is selectively delivered into the lower digestive tract. More particularly, a system which makes it possible to surely and quickly deliver the aimed substance to the lower digestive tract without being affected by pH change in the digestive tract due to change in bacterial flora. Compositions disintegrating in the lower digestive tract characterized by containing a compound A, which has a molecular weight of 1000 or less and has a disulfide bond, and a polymer B, which has a molecular weight exceeding 1000 and is digested by enteric bacteria and/or undergoes softening, swelling or dissolution due to a decrease in pH; molded products with the use of these compositions; and preparations with the use of these molded products.