The possible relationship between metabolism and psychotomimetic activity among the methoxylated l-phenyl-2-aminopropanes led to our investigation of the in vitro 0- demethylation of 1-(2, 5-dimethoxy-4-rnethylphenyl)-2-aminopropane (1, DOM, STP). Employing a sensitive and highly selective stable isotope dilution assay, we observed that rabbit liver homogenates biotransform the amine 1 to its 2-0-demethyl, 5-0-demethyl, and ...