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.