Methysergide is also referred to as 1-methyl-d-lysergic acid-butanolamide, or UML-491. It differs from LSD by a methyl group on the indole Nitrogen and substitution of butanol for two ethyl groups on the amide linkage.
Methysergide is capable of producing a state of mind like LSD, judging by human reports and its its effect on fish, though methysergide is less potent than LSD. According to Abramson, a methysergide reaction is slightly longer-lasting, by 2-3 hours, than a typical LSD reaction. A trip on methysergide produces mental disorientation, insomnia, giddiness, a dreamy state, distortion of body image and apprehension.
Methysergide, psilocybin, and LSD were compared in 4 subjects. One of them felt that the experience was about half as severe as a LSD reaction, but in another subject, 3.5 milligrams of methysergide produced a full blown, typical LSD reaction equal to 25 micrograms of LSD. The table below lists the threshold dose of methysergide for each subject, felt to be equivalent to a 25 ug dose of LSD.
Methysergide is about as potent as psilocybin. Human subjects responded to an average threshold dose of 3.4 mg psilocybin, and an average threshold dose of 4.3 mg or more of methysergide. When the effects of LSD, methysergide, and psilocybin were compared in humans, psilocybin was 135X less potent than LSD, and methysergide was 170X less potent than LSD. A diminishment of potency is seen also in fish. Methysergide produces the fish surfacing reaction, but it is 250X less potent than LSD.
Abramson H. A. and A. Rolo (1965). Lysergic acid diethylamide (LSD-25). 38. comparison with action of methysergide and psilocybin on test subjects. The Journal of Asthma Research 3, 81-96. DOI:10.3109/02770906509106904