High Quality Content by WIKIPEDIA articles! Zacopride is a potent antagonist at the 5HT3 receptor and an agonist at the 5HT4 receptor. It has anxiolytic and nootropic effects in animal models, with the (R) enantiomer being the more active form. It also has antiemetic and pro-respiratory effects, both reducing sleep apnoea and reversing opioid-induced respiratory depression in animal studies.