Chemical laxatives
Chemical laxatives are substances that stimulate the intestine and are produced industrially. Chemical laxatives are mainly the so-called triarylmethane derivatives such as bisacodyl and sodium picosulfate. Bisacodyl is a substance that is only sparingly soluble in water and must first be absorbed from the intestine into the blood and from there into the liver.
In the liver, the sparingly water-soluble bisacodyl is turned into a water-soluble substance which is then released back into the intestine. This process is called the enterohepatic circulation (entero=intestine; hepatic= liver). Once in the intestine, the bisacodyl is converted by the intestinal bacteria into its active substance, which cannot leave the intestine and enter the bloodstream.
This creates a concentration equilibrium, i.e. an osmotic pressure, due to which water flows into the intestine and makes the stool more fluid and slippery. Since the bisacodyl must first pass from the intestine to the liver and from there back into the intestine, the effect only occurs after about 10-12 hours. The bisacodyl is more quickly effective if it is administered directly into the rectum in the form of a suppository.
Here the effect usually occurs within one hour. Sodium piosulfate also develops its effect much faster than bisacodyl, because it only needs 4-10 hours to take effect when administered in tablet form, although, like bisacodyl, it must pass through the so-called enterohepatic circulation to be activated.
