Category Archives: reuptake inhibitors

HDMP-28 / Methylnaphthidate


HDMP-28 is a methylphenidate (ritalin, concerta) analogue which replaces the phenyl moiety with a naphthyl moiety.

Methylphenidate and HDMP-28

Methylphenidate and Methylnaphthidate


The modification confers a theoretical increase in SERT affinity, making effects closer to cocaine, and also theoretically gives increased potency over methylphenidate.

Despite being known about in scientific literature for many years, HDMP-28 is unusual in that it did not come to market until 2014. This is in stark contrast to many other known recreational drug analogues which were primarily surrected from the literature between 2010-2013.

The naphthyl moiety has caused some concern with comparisons drawn to naphthalene, but in the same way that we do not compare phenethylamines to benzene these concerns are not valid. The similar duration to methylphenidate offers additional reassurance, suggesting that the primary metabolic route is to the (naphthyl)ritalinic acid; which will be readily excreted.

Reports are still relatively scarce at this point and I struggled to find any which did not involve other drugs or multiple doses.

Dose: 30-60 mg

Duration: 5-7 Hours, Oral


10:14 – HR 67 bpm
10:15 – 34.8mg placed in mouth with water. There is an obvious taste of naphthalene but I press on because the “characteristic odor is detectable at concentrations as low as 0.08 ppm by mass”. Other than this it is not the most bitter of compounds.
10:40 – Maybe I am more focused and maybe there is a mood lift but it is mild and could be placebo
10:44 – Some tingles and definitely a mood lift so it wasn’t placebo
10:56 – Nothing more than that though
11:21 – Noticeably increased focus, a good functional level
11:43 – I am pretty engrossed in playing with my vape making some ejuices
12:03 – My girlfriend comes home. I am still feeling quite productive and chat to her while fixing a mirror
12:53 – I manage to eat a serving of protein shake/oats without issue despite not being hungry
13:25 – We have great sex and I have no problems maintaining an erection though do last longer than normal
14:00 – I feel very serene lying in bed with her
14:16 – We chat for a bit longer and she leaves to visit her mother. I still feel nicely stimulated, perhaps more noticeably than when she arrived.
14:35 – HR ~80bpm
14:43 – Not sure if I’m higher or just starting to feel a bit uncomfortable from coming down
15:11 – Certainly more noticeable headspace than earlier. Still not sure if it’s an enjoyable one.
15:22 – Not very good at deciding if I’m hot or cold
15:52 – Intensity of sensations have lessened
16:24 – Certainly on the way down now
17:19 – Have been thoroughly engrossed in design work for a new project, probably sober now. No comedown noticeable.

Conclusion: At this dose it is a mild stimulant but there is no hint of the promises made by the available pharmacological data. It certainly appears less potent than methylphenidate, a good 66% less. Additionally the serotonergic affinity seems unchanged at best, with no signs of real recreational potential. Certainly the lack of comedown warrants experimentation at higher doses, and the increased duration makes it miles better than ethylphenidate, but I won’t be expecting greatness from this one.