HDMP-28 (Methylnaphthidate) CAS # 219915-69-2 is a stimulant drug based on piperidine, closely related to methylphenidate, but with naphthalene substituted by the benzene ring. It is a potent inhibitor of dopamine reuptake, with many times the potency and short duration of action of methylphenidate, N, O-Dimethyl-4-(2-naphthyl)piperidine-3-carboxylate, is a structural isomer of another potent dopamine reuptake inhibitor.