Mescaline, lysergic acid diethylamide and psilocybin: Comparison of clinical syndromes, effects on color perception and biochemical measures

Summary Mescaline, lysergic acid diethylamide (LSD-25) and psilocybin were studied in 20 screened subjects, 18 receiving all three drugs. Drugs were administered under similar test conditions, doses were constant between drugs and subjects, assignments to drug followed a latin-square sequence, and subjects were unaware of the drug given on each trial. Clinical syndromes were assessed by a questionnaire completed by the subjects following each drug trial. Color perception was studied by means of both adequate and inadequate stimuli for eliciting color phenomena, measurements being taken before and two hours after drug was administered. A number of selected biochemical and physiologic measurements were also made at similar times. Clinical syndromes were comparable in kind and degree from all three drugs, that from mescaline being most pronounced. Somatic manifestations predominated, psychotomimetic symptoms (other than visual hallucinations) being relatively uncommon. Color perception was not much altered when adequate stimuli were used, but color phenomena were appreciably enhanced from inadequate stimuli. Minor differences in color perceptual effects were noted between the three drugs, but similarities were greater. Each of the three drugs significantly decreased urinary excretion of inorganic phosphorus, increased plasma free fatty acids and decreased total circulating eosinophils. Of the other biochemical measurements made, only one other significant change was noted; an increase in copper oxidase activity after psilocybin. The three psychotomimetic drugs were quite comparable in the areas studied. One might assume that they have many common mechanisms of action despite their chemical differences.