Purity >99% by HPLC Heavy Metals: Less than 20 ppm . Antidiarrheal agent. It inhibits peristaltic activity by a direct effect on the circular and longitudinal muscles of the intestinal wall. It is a non-selective Ca2+ channel blocker and binds with high affinity to μ opioid receptors. Evidence also suggests that at higher concentrations it binds to NMDA receptors and to calmodulin.