The variability of orocecal transit time evaluated by the salicylazosulphapyridine/sulphapyridine method

The inter- and intrasubject variability of the orocecal transit time assessed by the salicylazosulphapyridine/sulphapyridine test was examined. Nine healthy males attended on 3 occasions. Between-days comparison gives highly reproducible transit times for the subjects considered as a group (median values and their 95%-confidence limits): 4.0 (3.5-4.5), 4.5 (3.5-5.0), and 4.5 (3.0-4.5) hours, respectively. Fifty-nine per cent of the individual transit times amounts to 4.0 or 4.5 hours. Within subject comparison revealed marked differences for 4 of the volunteers. The maximum between-days differences observed were 1.0 (3 subjects) and 2.5 hours, respectively. Similar results of variability become evident regarding the area under the sulphapyridine concentration-time curves. In conclusion, it appears reasonable to use this method in assessing e.g. the effects of drugs on the transit time in crossover studies.