Most drugs introduced into the GIT are absorbed into the stomach and/or the small intestine according to their chemical character. Some drugs (their number is on the increase) require targeted supply to a certain site in the GIT if their biological activity is to be manifested and made use of. Fulfilling this condition, which concerns primarily peptides and proteins, requires adjustments of dosage forms. Much effort is put forth to shift absorption into the large intestine (colon), which is advantageous from the viewpoint of circadian biorhythms.