MLD-41, also known as 1-methyl-LSD, is a psychedelic drug of the lysergamide family related to lysergic acid diethylamide (LSD). It has about 33% of the psychoactive potency of LSD. It has been studied with regard to cross-tolerance with LSD. Extensive metabolism of other 1-methylated lysergamides to their secondary amine derivatives, for instance methysergide (1-methylmethylergometrine) conversion into methylergometrine, has been observed.