HDMP-28 or methylnaphthidate is a stimulant drug of the piperidine and naphthylaminopropane groups, closely related to methylphenidate (Ritalin), but with the benzene ring replaced by naphthalene. It is a potent dopamine reuptake inhibitor, with several times the potency of methylphenidate and a short duration of action, and is a structural isomer of another potent dopamine reuptake inhibitor, N,O-Dimethyl-4-(2-naphthyl)piperidine-3-carboxylate. It has been sold as a designer drug since around 2015.
Most of the TMP analogs of HDMP-28 have SERT Ki values in the range >10,000 and so are selective for dopamine and noradrenaline reuptake, with little or no effect on serotonin. HDMP-28 has high affinity to SERT, and so behaves as a triple reuptake inhibitor.
D.R. is the discrimination ratio = [3H]DA ÷ [3H]CFT.
A low D.R. indicates more addictive, whereas a high D.R. indicates low propensity for self-administration.
HDMP-28 is illegal in Switzerland as of December 2015.