HDMP-28 or methylnaphthidate is a stimulant drug of the piperidine and naphthylaminopropane groups, closely related to methylphenidate, 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,[1] and is a structural isomer of another potent dopamine reuptake inhibitor, N,O-Dimethyl-4-(2-naphthyl)piperidine-3-carboxylate.

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.

is the discrimination ratio = [3H]DA ÷ [3H]CFT.