CompletedPhase 1

Role of the Serotonin 5-HT2A Receptor in Mescaline-induced Altered States of Consciousness

NCT04849013 · MDR · University Hospital, Basel, Switzerland

Closed to entry

Status

Not accepting participants

Phase 1

Phase

Target enrolment

Study sites

Outside the US

What it is testing

Summary

Mescaline (the active substance in Peyote and San Pedro cacti) is a classic and long known serotonergic psychedelic substance (hallucinogen) that is widely used for recreational, spiritual, and/or ethno medical purposes. Despite its long history, modern data on the acute effects of mescaline on human is lacking. Mescaline produces prototypical psychedelic effects, similar as lysergic acid diethylamide (LSD) and psilocybin. The serotonin 2A (5-HT2A) receptor is thought to primarily mediate acute alterations of consciousness induced by LSD and psilocybin. However, the contributory role of the 5-HT2A receptor in mescaline-induced alterations of consciousness is unclear. Using 5-HT2A receptor antagonist ketanserin, the psychedelic experience induced by LSD and psilocybin can be attenuated and shortened. The present study therefore explores the role the 5-HT2A receptor in mescaline-induced altered states of consciousness using escalating doses of mescaline and the 5-HT2A receptor blocker ketanserin administered before a high dose of mescaline. Objective: The present MDR-study will characterize the subjective effects of different doses of mescaline using modern psychometric instruments and examine the contribution of the 5-HT2A receptor in the mescaline-induced alterations of consciousness. Design: Double-blind, placebo-controlled, 6-period cross-over design with six treatment conditions. 1) Placebo (Pla + Pla), 2) 100 mg mescaline (Pla + 100mg mescaline), 3) 200 mg mescaline (Pla + 200mg mescaline), 4) 400 mg mescaline (Pla + 400mg mescaline), 5) 800 mg mescaline (Pla + 800mg mescaline), and 6) 40mg ketanserin and 800mg mescaline (Ket + 800mg mescaline). Participants: 16 healthy participants aged ≥ 25 and ≤ 65 years (8 female, 8 male)

Summary as written by the trial’s own sponsor and published on ClinicalTrials.gov API v2. It is the sponsor’s description, reproduced unedited, not an assessment by this site.

What counts as success

Primary outcome measures

Altered States of Consciousness
Measured over 18 months

A trial succeeds or fails on its primary outcome, declared in advance. Everything else it reports is secondary by definition.

Who can take part

Eligibility, as published

25 Years to 65 Years

Ages

All

Sex

Accepted

Healthy volunteers

Inclusion Criteria: 1. Age between 25 and 65 years old 2. Sufficient understanding of the German language 3. Understanding of procedures and risks associated with the study 4. Willing to adhere to the protocol and signing of the consent form 5. Willing to refrain from the consumption of illicit psychoactive substances during the study 6. Abstaining from xanthine-based liquids from the evenings prior to the study sessions to the end of the study days 7. Willing not to drive a traffic vehicle or operate heavy machinery within 48 hours after substance administration 8. Willing to use double-barrier birth control throughout study participation 9. Body mass index between 18-29 kg/m2 Exclusion Criteria: 1. Chronic or acute medical condition 2. Current or previous major psychiatric disorder 3. Psychotic disorder or bipolar disorder in first-degree relatives 4. Hypertension (\>140/90 mmHg) or hypotension (SBP10 cigarettes/day) 5. Hallucinogenic substance use (not including cannabis) more than 20 times or any time within the previous two months 6. Pregnancy or current breastfeeding 7. Participation in another clinical trial (currently or within the last 30 days) 8. Use of medication that may interfere with the effects of the study medication 9. Tobacco smoking (\>10 cigarettes/day) 10. Consumption of alcoholic beverages (\>20 drinks/week)

Where

1 study site

Facility	City	Region	Country
University Hospital Basel, Clinical Trial Unit	Basel	Canton of Basel-City	Switzerland

On the registry

Contact the trial directly

This site does not enrol anyone and is not involved in this trial. To ask about taking part, use the sponsor’s own contact details on the official registry record, which is also where the most current version of everything above lives.

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NCT04849013 on ClinicalTrials.gov →

Last updated in the registry 2023-03-29. Registry records change; this page reflects the data build of 2026-08-25.

Where this trial sits

Substance

Mescaline

All 48 trials from University Hospital, Basel, Switzerland →