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Psychedelic Effects in Healthy VolunteersEarly Phase 1PsilBlock1NCT07565493

Psilocybin Administration With 5-HT1a Blockade

A Early Phase 1 study testing Pindolol and Psilocybin in people with Psychedelic Effects in Healthy Volunteers, run by Johns Hopkins University at 1 site in United States.

Recruiting

Looking for participants now. Contact the study team or a site below to ask about taking part.

Sites and contacts
Official record
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Trial summary

The purpose of this study is to assess the effects of 5-HT1A receptor blockade on the acute subjective effects of psilocybin, as measured through subjective survey measures and acute electroencephalography (EEG). Read more about this study

Who is it for?
Ages 21 to 60 yearsHealthy volunteers can take part
What is being tested?
Pindolol and Psilocybin
Type of treatment
Pill or oral medicine
Could I receive a placebo?
Yes, some participants may receive a placebo
How many people
18 participants
Where
1 siteUnited States
Study dates
12 Aug 2026to 15 Jun 2028
Phase
Early Phase 1
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 21 to 60 years
  • All sexes
  • Healthy volunteers accepted
  • Adult

Who may be able to join

  • 21 - 60 years old
  • Must give written or electronic informed consent
  • Must have at least a high-school level of education or equivalent (e.g. GED) and are fluent in English
  • Must be healthy and psychologically stable as determined by screening for medical and psychiatric problems via a personal interview, a medical questionnaire, a physical examination, an electrocardiogram (ECG), and routine medical blood and urinalysis laboratory tests
  • Must agree not to take any as needed (PRN) medications on the mornings of drug sessions
  • Must agree not to take sildenafil (Viagra®), tadalafil, or similar medications within 72 hours of each drug administration.
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  • Must agree to refrain from using all psychoactive substances within 24 hours or 5 elimination half-lives (whichever is greater) before psilocybin administration. Caffeine is the exception.
  • Must have a negative urine toxicology report on the same day as drug dosing.
  • Who are female and of child-bearing potential and are sexually active, must agree to use highly effective means of birth control (i.e. implants, injectables, combined oral contraceptives, progestin-containing intrauterine device (IUD) or vasectomized partner) for the duration of this study.
  • Who are male and sexually active, must agree to use contraception and refrain from sperm donation within 90 days of completing dosing sessions. Effective methods of contraception are barrier, hormonal, and sterilization methods.

Who cannot join

  • Are currently taking a medication with any significant pharmacokinetic or pharmacodynamic interactions with pindolol (e.g. beta-blockers or other anti-hypertensive medications).
  • Have a history of orthostatic hypotension or low blood-pressure.
  • Have elevated transaminases (2x the upper limit of normal)
  • Have a Child-Pugh score that falls within classes B or C.
  • Are pregnant (as indicated by a positive urine pregnancy test assessed at intake and before each drug session) or nursing.
  • Have cardiovascular conditions: coronary artery disease, stroke, angina, uncontrolled hypertension, a clinically significant ECG abnormality (e.g. atrial fibrillation, corrected QT interval (QTc) > 450 msec), artificial heart valve, symptomatic valvopathy, history of pulmonary hypertension or transient ischemic attack (TIA) in the past year; systolic blood pressure > 139, diastolic blood pressure > 89
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  • Have epilepsy or a history of seizures
  • Have insulin-dependent diabetes; if taking oral hypoglycemic agent, then no history of hypoglycemia
  • Are currently taking on a regular (e.g. daily) basis any medications having a centrally acting serotonergic effect, including monoamine oxidase inhibitors (MAOIs). For individuals who have intermittent or PRN use of such medications, psilocybin sessions will not be conducted until at least five half-lives of the agent have elapsed after the last dose.
  • Have a current diagnosis of schizophrenia spectrum disorders
  • Have a current diagnosis of bipolar spectrum disorders
  • Have a current diagnosis of major depressive disorder or Generalized Anxiety Disorder
  • Have a current diagnosis or history of substance induced psychotic disorder
  • Have a current DSM-5 moderate or severe alcohol or drug use disorder (excluding caffeine and nicotine)
  • Have a first degree relative with bipolar I disorder, or schizophrenia spectrum disorder.
  • Have a psychiatric condition judged to be incompatible with establishment of safe exposure to psilocybin.
  • Have a BMI ≥ 40
  • Report a known history of sleep apnea, symptoms indicative of sleep apnea, or have an Apnea-Hypopnea Index (AHI) > 15, or STOP BANG >5
  • Taking prescribed hypnotics or other medications known to alter sleep physiology: i.e., Z-drugs, Benzodiazepines, Orexin Agonists or Antagonist, Beta Blockers.
  • Regularly taking over-the-counter sleep aids (inc. melatonin and diphenhydramine) and unwilling to abstain during the study.
  • Insomnia Severity Index ≥ 10

Trial locations and contacts

1 site in 1 country. Contact the study team or a site near you to ask about taking part.

Zarmeen Zahid, PhD contact

667-208-8099

psilblock@jh.edu

United States1 site, 1 recruiting

  • Center for Psychedelics and Consciousness Research

    Baltimore, Maryland, 21224-5010

    Zarmeen Zahid, PhD, 667-208-8099, psilblock@jh.edu

    Sandeep M Nayak, MD

    Recruiting

Other trials in United States

About this study

The purpose of this study is to assess the effects of 5-HT1A receptor blockade on the acute subjective effects of psilocybin, as measured through subjective survey measures and acute electroencephalography (EEG). Further, the investigators will assess the effects of psilocybin on post-acute sleep and dreaming through the use of sleep EEG and sleep and dream diaries.

Read the detailed description

This double-blind, randomized, cross-over study (N = 18) will administer a moderate dose of psilocybin trihydrate (18 mg, equivalent to 15 mg psilocybin anhydrate), with pindolol (30 mg), or placebo to assess the effects of 5-HT1A receptor blockade on the acute subjective effects and the acute neurophysiological effects of psilocybin through the use of self-report measures and acute EEG. Participants will also complete sleep and dream diaries 10 days prior to and 10 days following each drug administration session as well as wear an at-home sleep EEG device for 5 days prior to and 5 days following each drug session. This study aims to understand the mechanistic basis of the perceptual changes in the altered state of consciousness induced by psilocybin as well as its effects on post-acute sleep and dreaming.

Being tested
Pindolol, Placebo, Psilocybin
Keywords
Psilocybin, Sleep, Dreaming, EEG, 5-HT1A, Antagonism, Altered state of consciousness, Subjective experience, Serotonin receptor, Psychedelic

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • PindololDrug

    Pindolol is a 5-HT1A antagonist drug that will be used as a pharmacological probe for the mechanism of acute subjective effects in the altered state of consciousness induced by psilocybin.

  • PlaceboDrug

    Also called Microcrystalline cellulose placebo

    Microcrystalline cellulose capsules, identical in appearance to the active treatment, containing no pharmacologically active ingredients, will be administered as an inert placebo comparator.

  • PsilocybinDrug

    Psilocybin is a tryptamine psychedelic with 5-HT2A agonist activity. The psilocybin-induced altered state of consciousness is characterized by changes in sensory perception, cognition, and induction of mystical-type experiences. These subjective effects will be assessed in each dosing session.

Study groups in NCT07565493
Study groupRoleWhat they receive
Psilocybin co-administered with placeboPlacebo comparatorPsilocybin will be co-administered with microcrystalline cellulose placebo.
Receives: Drug: Placebo; Drug: Psilocybin
Psilocybin co-administered with pindololExperimentalPsilocybin will be co-administered with 5-HT1A antagonist pindolol.
Receives: Drug: Pindolol; Drug: Psilocybin

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Mystical Experiences Questionnaire

    Assess changes in intensity of the subjective effects induced by psilocybin with co-administration of a 5-HT1A antagonist, pindolol as measured through the mystical experience questionnaire. Scores can range from 0-150 with a higher score indicating a more intense mystical-type experience.

    Measured: From the first dosing session to the end of the second dosing session, approximately 10 days

Secondary outcomes (1)

  1. Change in alpha power (Spectral Power)

    Assess changes in neural measures of drug intensity acutely using EEG, specifically global change in alpha power.

    Measured: From the first dosing session to the end of the second dosing session, approximately 10 days

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted4 May 2026
  2. Study start12 Aug 2026
  3. Primary completion15 Jun 2028 (estimated)
  4. Study completion15 Jun 2028 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Early Phase 1
Primary purpose
Basic science
Allocation
Randomised
Intervention model
Crossover
Model description
Within subjects crossover design with 2 conditions: Psilocybin co-administered with placebo, and psilocybin co-administered with pindolol.
Masking
Triple blind
Who is masked
Participant, Investigator, Outcomes assessor
Enrolment
18 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT07565493
Sponsor's protocol ID
IRB00478908
Acronym
PsilBlock1
Status last verified
Sep 2026
First submitted
27 Apr 2026
Last updated
14 Sep 2026
Results posted
No
Data monitoring committee
No
FDA-regulated drug
Yes
FDA-regulated device
No
Individual data sharing
Yes: De-identified data with no participant information will be shared on an open science platform to allow for independent analysis by other researchers. Subjective survey data, acute EEG, and sleep EEG data will be shared.

Publications

  • Strassman RJ. Human psychopharmacology of N,N-dimethyltryptamine. Behav Brain Res. 1996;73(1-2):121-4. doi: 10.1016/0166-4328(96)00081-2.

    PubMed 8788488

Questions about this trial

What is this clinical trial studying?

A Early Phase 1 study testing Pindolol and Psilocybin in people with Psychedelic Effects in Healthy Volunteers, run by Johns Hopkins University at 1 site in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 10 inclusion and 21 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: looking for participants now, as of the sponsor's last update on 14 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Early Phase 1 (sometimes called Phase 0) studies give a very small amount of a treatment to a few people, mainly to see how the body handles it.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

Contact Zarmeen Zahid, PhD (667-208-8099, psilblock@jh.edu), or a site near the patient. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Mystical Experiences Questionnaire (time frame: From the first dosing session to the end of the second dosing session, approximately 10 days). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT07565493, which also lists 1 linked publication.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 14 Sep 2026.

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