3,4,5-Trimethoxytranylcypromine (TMT), also known as MCPA as well as trans-2-(3,4,5-trimethoxyphenyl)cyclopropylamine, is a possible psychedelic drug of the phenethylamine, scaline, and phenylcyclopropylamine families related to mescaline (3,4,5-trimethoxyphenethylamine). It is a cyclized phenethylamine and the analogue of mescaline in which the ñ and ò positions of the ethyl side chain have been cyclized to form a cyclopropane ring. The drug may also be thought of as a structural hybrid between mescaline and the antidepressant tranylcypromine.
In his book PiHKAL (Phenethylamines I Have Known and Loved), Alexander Shulgin reported that TMT produced no central effects at a dose of 13mg orally. Higher doses were not assessed.
TMT has been reported to produce mescaline-like effects in animals with similar or slightly greater potency than mescaline but a slightly shorter duration. TMT is the trans isomer of a pair of cis and trans isomers, and it is specifically the trans isomer that is active.
TMT was first described in the scientific literature by G. C. Walters and P. D. Cooper in 1968. Alexander Shulgin subsequently described evaluating a low dose of TMT in humans in his 1991 book PiHKAL (Phenethylamines I Have Known and Loved). TMT was one of the earliest psychedelic-related cyclized phenethylamines to be evaluated. Subsequently, the much more potent 2,5-dimethoxy-4-methylphenylcyclopropylamine (DMCPA) was developed.
TMT is not a controlled substance in Canada as of 2025.