Site-specific drug delivery systems within the gastro-intestinal tract: from the mouth to the colon.

Delivery of drugs by the oral route remains the most spread route to administer medicines to patients. The manuscript takes into consideration the most important organs of the digestive system (mouth, oesophagus, stomach, small intestine and colon), their size, physiology and transit patterns of dosage forms while travelling in the digestive tract. For each organ several strategies are considered, namely, adhesion, chemical modification of drug and/or excipient moieties, technological features of dosage forms (e.g. porosity, disintegration time), pH variations or transit times. The manuscript considers strategies that are commonly used in practice for long-term administration of drugs, without interfering with human physiology, and feasible industrially.