Comparison of canine and human gastrointestinal physiology

In this review, the gross physiology of the gastrointestinal tract of dogs is compared with that of humans, particularly as it pertains to drug absorption and dosage-form performance. Gastrointestinal (GI) motility and pH are the main parameters considered. Although similar motility patterns and pH profiles prevail in the two species for the most part, there are some differences that could affect the time profile and extent of drug absorption. These include slower gastric emptying in the fed state, faster small intestine transit, and higher and more variable intestinal pH in dogs compared with humans. An attempt is made to identify drug and dosage-form properties that would lead to differences in drug absorption in the two species, e.g., drug physicochemical properties, dosage-form size, and pH dependency of dosage-form release characteristics.