2C-Se, also known as 4-methylseleno-2,5-dimethoxyphenethylamine, is a psychedelic drug of the phenethylamine and 2C families. It was originally named by Alexander Shulgin as described in his 1991 book PiHKAL (Phenethylamines I Have Known and Loved). Shulgin listed its dose as perhaps 100 mg orally and its duration as 6 to 8 hours. Its onset was 45 minutes, peak effects occurred after 1.5 hours, and doses of 50 to 70 mg orally produced threshold effects. Shulgin considered 2C-Se to be around three times the potency of mescaline, but was too concerned about toxicity to test it extensively, though he considered it noteworthy as the only psychedelic drug to contain a selenium atom. 2C-Se was first described in the literature by Shulgin in PiHKAL in 1991.