hdep-28 hdep-28 hdep-28 or ethylnaphthidate is a piperidine based stimulant drug, closely related to ethylphenidate, but with the benzene ring replaced by naphthalene. it is even more closely related to hdmp-28, which acts as a potent serotonin–norepinephrine–dopamine reuptake inhibitor with several times the potency of methylphenidate and a short duration of action. hdep-28legal statuslegal status ca: schedule iii de: npsg (industrial and scientific use only) uk: class b identifiers iupac name ethyl (naphthalen-2-yl)(piperidin-2-yl)acetate cas number2170529-69-6pubchem cid91844468chemspider52085106uniia8326sh248chemical and physical dataformulac19h23no2molar mass297.398 g·mol−13d model (jsmol)interactive image smiles ccoc(=o)c(c1ccccn1)c2ccc3ccccc3c2 inchi inchi=1s/c19h23no2/c1-2-22-19(21)18(17-9-5-6-12-20-17)16-11-10-14-7-3-4-8-15(14)13-16/h3-4,7-8,10-11,13,17-18,20h,2,5-6,9,12h2,1h3key:otqvtbphzrartl-uhfffaoysa-n legality hdep-28 was banned in the uk as a temporary class drug from june 2015 following its unapproved sale as a designer drug, alongside 4-methylmethylphenidate.