Phenolphthalein stimulates the formation of histamine, 5-hydroxytryptamine and prostaglandin-like material by rat jejunum, ileum and colon.

The effects of phenolphthalein on the formation of histamine, 5-hydroxytryptamine(5-HT) and prostaglandin-like material by rat intestine were examined in vivo. Phenolphthalein, in a dose that causes laxation increased the formation of histamine, 5-HT and prostaglandin-like material, and indomethacin reduced these increases. The data support the idea that the laxative effect of phenolphthalein is due to increased intestinal production of prostaglandin, histamine and 5-HT.