N-butyl hyoscine exerts local spasmolytic effect in the small and large bowel of the conscious dog.

The spasmolytic activity of N-Butyl Hyoscine (NBH) (1) has been investigated in conscious dogs provided with ileal or colonic Thiry fistulas in which motility was stimulated by intraluminal distension. In ileal motility experiments, phasic motility index (PMI), intestinal tonus, contraction frequency and heart rate were monitored. Intravenous administration of NBH (10 to 100 micrograms/kg) depressed PMI (ED50 35.1 micrograms/kg) and the other motility parameters. Heart rate increases were observed at 100 micrograms/kg. Application of NBH directly into the fistula (300 to 3000 micrograms/kg) caused a long-lasting, potent inhibition (31-72%) of PMI; tonus and contraction frequency were only slightly affected, while heart rate was not altered. When NBH was administered into an ileal fistula adjacent to the one from which motility was recorded, changes of PMI and other parameters were observed only after a massive dose of the drug (10000 micrograms/kg). In colonic fistula experiments, intraluminal NBH administration (300 to 3000 micrograms/kg) depressed colonic motility (39-59%), without affecting heart rate. It is concluded that NBH present in the intestine, although poorly absorbed, exerts local spasmolytic action.