CompletedEarly Phase 1

Role of the Serotonin 5-HT2A Receptor in LSD-induced Altered States of Consciousness (LDR-Study)

NCT03321136 · LDR · University Hospital, Basel, Switzerland

Closed to entry

Status

Not accepting participants

Early Phase 1

Phase

Target enrolment

Study sites

Outside the US

What it is testing

Summary

Serotonin receptors, especially the 5HT2A receptor, are thought to be involved in the effects of various recreationally used psychedelic substances such as LSD. LSD potently stimulates the 5-HT2A receptor but also 5-HT2B/C, 5-HT1 and dopaminergic receptors. LSD induces acute transient alterations in waking consciousness including visual perceptual alterations, audio-visual synesthesia, derealization and depersonalization. LSD has therefore been used as experimental tool ("psychotomimetic") in modern psychiatric research to study psychotic-like states and model psychosis in healthy subjects \[1-5\]. However, the dose-effects of 5-HT2A receptor stimulation by LSD has not yet been studied. Additionally, there is still very limited data to what extent the 5HT2A receptor contributes to LSD's effects and its role in the mediation of the full response to LSD at a high dose is unclear. A recent experimental human study showed the 5-HT2A receptor antagonist ketanserin fully blocked the subjective effects of a moderate dose of 100 µg of LSD \[6\]. But, whether the effects of a high 200 µg oral dose of LSD can be blocked by the selective pharmacological 5-HT2A antagonist ketanserin remains to be tested to confirm the critical role of the 5-HT2A receptor in more pronounced alterations of consciousness and perception. The present study therefore explores the role the 5-HT2A receptor in LSD-induced altered states of consciousness using escalating doses of LSD and the 5-HT2A receptor blocker ketanserin administered before a high dose of LSD.

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. 2. Understanding of the German language. 3. Understanding the procedures and the risks associated with the study. 4. Participants must be willing to adhere to the protocol and sign the consent form. 5. Participants must be willing to refrain from taking illicit psychoactive substances during the study. 6. Participants must be willing to drink only alcohol-free liquids and no coffee, black or green tea, or energy drink after midnight of the evening before the study session, as well as during the study day. 7. Participants must be willing not to drive a traffic vehicle or to operate machines within 48 h after substance administration. 8. Women of childbearing potential must have a negative pregnancy test at the beginning of the study. Pregnancy tests are repeated before each study session. 9. Women of childbearing potential must be willing to use double-barrier birth control 10. Body mass index 18-29 kg/m2. Exclusion Criteria: 1. Chronic or acute medical condition 2. Current or previous major psychiatric disorder 3. Psychotic disorder in first-degree relatives 4. Illicit substance use (with the exception of cannabis) more than 10 times or any time within the previous two months. 5. Pregnant or nursing women. 6. Participation in another clinical trial (currently or within the last 30 days) 7. Use of medications that may interfere with the effects of the study medications (any psychiatric medications) 8. Tobacco smoking (\>10 cigarettes/day) 9. Consumption of alcoholic drinks (\>10/week)

Where

1 study site

Facility	City	Region	Country
University Hospital	Basel	—	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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NCT03321136 on ClinicalTrials.gov →

Last updated in the registry 2019-08-28. Registry records change; this page reflects the data build of 2026-08-25.

Where this trial sits

Substance

All 48 trials from University Hospital, Basel, Switzerland →