Direct Comparison of Altered States of Consciousness Induced by LSD, Psilocybin, and DMT in Healthy Participants

Lysergic acid diethylamide (LSD), psilocybin, and N,N-dimethyltryptamine (DMT) are serotonergic hallucinogens (psychedelics) and currently investigated as therapeutic tools for the treatment of various psychiatric disorders. They are usually administered in a dose range which induces an alteration of consciousness via the stimulation of the serotonin (5-HT)2A receptor. However, there are differences in the receptor activation profiles between the three substances that may induce different subjective effects. Moreover, they exhibit different pharmacokinetic qualities. In comparative studies of LSD and psilocybin blinding was impaired by the different duration of subjective effects. This study aims to ensure blinding by ending all experiences at the same time with the 5HT2A antagonist ketanserin. Moreover, no study has yet directly compared DMT to LSD and psilocybin. The DMT infusion will be modeled in accordance with the course of an oral LSD and psilocybin administration. Therefore, the LPD-study compares the acute and subacute effects of LSD, psilocybin, and DMT while standardizing the time course and the duration of action for all substances.

Inclusion criteria

• Good understanding of the German language
• Understanding of procedures and risks associated with the study
• Willing to adhere to the protocol and signing of the consent form
• Willing to refrain from the consumption of illicit psychoactive substances during the study
• Willing not to operate heavy machinery within 48 h after administration of a study substance
• Willing to use effective birth control throughout study participation
• Body mass index 17 - 34.9 kg/m2

Exclusion criteria

• Relevant chronic or acute medical condition
• Current or previous major psychiatric disorder (e.g. psychotic disorder)
• Psychotic disorder or bipolar disorder in first-degree relatives
• Hypertension (SBP>140/90 mmHg) or hypotension (SBP<85 mmHg)
• Bradycardia (< 45 bpm)
• Prolonged QTc interval (males: >450 ms, females: >470 ms)
• AV block II° (Mobitz type and Webckebach type) and III°
• Hallucinogenic substance use (not including cannabis) more than 20 times or any time within the previous two months
• Pregnancy or current breastfeeding
• Participation in another clinical trial (currently or within the last 30 days)
• Use of medication that may interfere with the effects of the study medication
• Tobacco smoking (>10 cigarettes/day)
• Excessive consumption of alcoholic beverages (>15 drinks/week)