The method for the assessment of small intestinal transit time (SITT) in beagle dogs was investigated by using the time for the first appearance of sulfapyridine in the plasma (TFA) after oral administration of salicylazosulfapyridine (SASP). After administration of SASP into the small intestine or the cecum of anesthetized dogs, sulfapyridine (SP) was detected in the plasma only in the latter case. These results indicate that TFA could be an index of arrival time in the cecum, an index of SITT in dogs. A remarkable inter-individual variation of TFA was observed after oral administration of SASP to fasting dogs, and the mean value of TFA was about 3 h. As for intra-individual variation of TFA, both variable and less variable dogs were observed. TFA was prolonged significantly by atropine (0.1 mg/kg, i.v.) and shortened significantly by metoclopramide (0.5 mg/kg, i.v.). As the pharmacological modification of gastrointestinal motility was thus mirrored by TFA, SASP method is considered to be useful for the assessment of SITT in beagle dogs.
