Moxidectin-d 3 (CL-301423-d 3 ) is deuterium labeled Moxidectin. Moxidectin (CL301423) is an orally active macrolide (ML) anthelmintic for the prevention and control of heartworms and roundworms. Moxidectin is also a substrate of BCRP and P-glycoprotein (P-gp) in vivo, and is secreted into breast milk and effluxed from the host and parasite mediated by Bcrp1 and P-gp. This may be related to the presence of chemical residues in milk.