[Mode of action of bisacodyl (dulcolax) on isolated muscles of human colon (author's transl)].

The effects of bisacodyl (4,4-diacetyl-bis-hydroxyphenyl-pyridyl-(2)-methan, Dulcolax) on the tone of isolated muscle strips of human colon were examined. Maximal contractions achieved by 10 mug/ml of bisacodyl were quite comparable to those due to 1 mug/ml of acetylcholine, 1 mug/ml of histamine and 0.5 mug/ml of nicotine, respectively. However, peak contractions were attained with a greater latency and could not be prevented by the anticholinergic agent atropine, the H1-antihistaminic diphenhydramin or tetrodotoxin blocking axonal conduction. On the other hand, pretreatment with verapamil -- antagonizing calcium influx into the muscle cell -- abolished bisacodyl effects. These results provide evidence for a direct action of bisacodyl on smooth muscle cells of human colon.