Racecadotril-d5 is intended for use as an internal standard for the quantification of racecadotril by GC- or LC-MS. Racecadotril is a prodrug form of the neprilysin (NEP) inhibitor thiorphan. In vivo, racecadotril reduces or prevents castor oil-induced diarrhea without delaying intestinal transit in rats when administered at doses of 80 or 100 mg kg, respectively. It also decreases the duration of diarrhea and increases body weight gain in a neonatal gnotobiotic pig model of human rotavirus-induced diarrhea. Formulations containing racecadotril have been used in the treatment of acute diarrhea.