Suppression of laxative action of phenolphthalein by orally-administered indomethacin or aspirin

Oral administration of phenolphthalein produced a dose-dependent increase of wet faeces excreted by mice. The response to phenolphthalein was reduced by pretreatment with indomethacin, aspirin or polyphloretin phosphate (PPP), but not with benoxaprofen. These findings support the view that the effect of phenolphthalein may be suppressed by PG synthetase inhibitors (indomethacin, aspirin) and by PPP.