Psilocybin (active compound of "magic mushrooms") is a prototypical psychedelic substance that acts via agonism on serotonin (5-HT) 2A receptors. Psilocybin is rapidly metabolized into its active metabolite psilocin. Psilocybin is currently under investigation as potential treatment for various neuropsychiatric disorders. Psilocybin is also widely used for recreational purposes and as research tool in neuroscience. Besides its current clinical development, a clear characterization of the dose-response relationship of psilocybin is lacking. With the present study the investigators aim to close this knowledge gap by administering low (5mg) to high (40mg) single doses of psilocybin to healthy participants. Besides its agonism on 5-HT2A receptors, psilocin also binds to other receptors and inhibits serotonin transporters (SERT). To this data only few studies have investigated these effects and never at a high dose.
Psilocybin is widely used for recreational and spiritual purposes. Additionally Psilocybin is currently reused in experimental studies with healthy subjects and in studies investigating its effects on patients suffering from anxiety, depression, addiction personality disorders and other pathological conditions. The present PDR-study will characterize the subjective effects of different doses of psilocybin using modern psychometric instruments, explore the relationship between the plasma-concentration of psilocybin and its subjective effects, and examine the contribution of the 5-HT2A receptor in the psilocybin-induced alterations of consciousness in a mechanistic study in healthy subjects. Participants will recieve doses of 5, 10, 20, and 40 mg psilocybin, 40 mg of psilocybin with pretreatment of 40 mg ketanserin, and placebo (control for psilocybin). Placebo pretreatment (control for ketanserin) will be used for all psilocybin administrations without ketanserin. Administrations will be separated by at least 10 days and are in random and counter-balanced order.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
TRIPLE
Enrollment
16
40mg Ketanserin oral will be administered followed by 40mg Psilocybin.
Placebo oral followed by 40mg Psilocybin one hour later.
Placebo oral followed by 20mg Psilocybin one hour later.
Placebo oral followed by 10mg Psilocybin oral one hour later.
Placebo oral followed by 5mg Psilocybin one hour later
Oral Placebo followed by oral Placebo one hour later
Clinical Trial Unit
Basel, Canton of Basel-City, Switzerland
RECRUITING5 dimensions of altered state of consciousness (5D-ASC) total OAV score
Visual analog scale consisting of 94 items. Constructed of five scales and allows assessing mood, anxiety, derealization, depersonalization, changes in perception, auditory alterations, and reduced vigilance. Scales will be presented as 100 mm long horizontal lines marked with vertical lines by the participant.
Time frame: 10 hours after substance administration
Visual Analog Scales (VAS) good effect rating
VAS will be presented as 100 mm long horizontal lines marked with "not at all" on the left and "extremely" on the right. The following VAS items will be used: "any drug effect", "good drug effect", "bad drug effect", "drug high", "anxiety", "nausea", "feeling depressed", "alteration of vision", "alterations of hearing", "sounds seem to influence what I see", "alteration of sense of time", "the boundaries between myself and my surroundings seem to blur", "I gain insights into contexts that were previously were inscrutable to me", "talkative", "open", "trust" and "the context of my thought is personal/impersonal". Subjects will mark the scale with vertical lines.
Time frame: One hour before, right after and 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10 and 24 hours after substance administration
Adjective Mood Rating Scale AMRS
The adjective mood rating scale (AMRS or EWL60S) is a 60-item Likert scale that allows repeated assessment of mood in 6 dimensions: activation, inactivation, well-being, anxiety/depressed mood, extroversion and introversion, and emotional excitability.The AMRS consists of subscales measuring "activation", "positive mood", "extroversion", "introversion", "inactivation", and "emotional excitability.
Time frame: One hour before as well as 3, 6, 10 and 24 hours after substance administration
States of consciousness questionnaire (SCQ)
This 100-item questionnaire is rated on a six-point scale. Forty-three items embedded into this questionnaire comprise the Mystical Experience Questionnaire (MEQ). which is sensitive to the effects of psilocybin. The 43 items provide scale scores for each of seven domains of mystical experiences: internal unity (pure awareness, a merging with ultimate reality), external unity (unity of all things, all things are alive, all is one), sense of sacredness (reverence, sacred), noetic quality (encounter with ultimate reality, more real than everyday reality), transcendence of time and space, deeply felt positive mood (joy, peace, love), paradoxicality/ineffability (claim of difficulty in describing the experience in words). The investigators will also derived the four scale scores of the newly validated revised 30-item MEQ: mystical, positive mood, transcendence of time and space, and ineffability.
Time frame: 10 hours after substance administration
Phenomenological-Autobiographical-Existential Psychedelic Scale extended (PAE-PS-ext)
This questionnaire rates psychedelic experiences with a focus on phenomenological, autobiographical, and existential psychedelic experiences. The scale includes 12 main questions to be answered on a total of 78 sub-ordered visual rating scales (sub-ordered visual rating scales mostly only need to be answered when the answer to the main question is "yes"). The last major question with eight sub-ordered visual rating scales of the PAE-PS is on worldview/beliefs.
Time frame: This questionnaire is administrated once before the first substance day (during screening), and then again 10h after substance administration on everx study visit..
Acute autonomic effects I (blood pressure)
Blood pressure (systolic and diastolic) will be measured with an automatic oscillometric device.
Time frame: One hour before, right after and 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10 and 24 hours after substance administration
Acute autonomic effects II (heart rate)
Heart rate will be measured with an automatic oscillometric device.
Time frame: One hour before, right after and 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10 and 24 hours after substance administration
Acute autonomic effects III (body temperature)
Body temperature will be measured with an ear thermometer.
Time frame: One hour before, right after and 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10 and 24 hours after substance administration
Effect moderation by personality traits I (NEO-FFI)
Personality traits are known to affect subjective responses to psychoactive substances and are assessed for explorative future analysis of pooled data. The NEO Five Factor Inventory (NEO-FFI) is a self-description questionnaire with 60 items for the measurement of the "big five": neuroticism, extraversion, openness, agreeableness, and consciousness. It uses a 5-point Likert scale ranging from "completely disagree" to "fully agree".
Time frame: Screening
Effect moderation by personality traits II (FPI-R)
Personality traits are known to affect subjective responses to psychoactive substances and are assessed for explorative future analysis of pooled data. The Freiburger Personality Inventory (FPI-R) version comprises 138 items and covers 12 dimensions of personality: life satisfaction, social orientation, performance orientation, inhibition, excitability, aggressiveness, stress, physical complaints, health concerns, openness, as well as the secondary factors according to Eysenck's Extraversion and Emotionality (Neuroticism). It uses a 2-point scale ("true" and "not true").
Time frame: Screening
Effect moderation by personality traits III (SPF)
Personality traits are known to affect subjective responses to psychoactive substances and are assessed for explorative future analysis of pooled data. The Saarbrücker Persönlichkeitsfragebogen (SPF) defines empathy as the "reactions of one individual to the observed experiences of another." It assesses 28-items on a 5-point Likert scale ranging from "Does not describe me well" to "Describes me very well". The measure has 4 subscales (Perspective Taking, Fantasy, Empathic Concern, Personal Distress) each made up of 7 different items.
Time frame: Screening
Effect moderation by personality traits IV (HEXACO)
Personality traits are known to affect subjective responses to psychoactive substances and are assessed for explorative future analysis of pooled data. The HEXACO personality inventory is a six-dimensional model of human personality with 100 items.The six factors are: Honesty-Humility, Emotionality, Extraversion, Agreeableness, Conscientiousness and Openness to Experience.
Time frame: Screening
Effect moderation by personality traits V (DSQ-40)
Personality traits are known to affect subjective responses to psychoactive substances and are assessed for explorative future analysis of pooled data. The Defense Style Questionnaire (DSQ-40) can provide scores for 20 individual defenses, and scores for the three factors "mature", "neurotic", and "immature". Each item is evaluated on a scale from 1 to 9, where "1" indicates "completely disagree" and "9" indicates "fully agree".
Time frame: Screening
Psychological Insight Questionnaire (EBI+)
Assesses the degree of psychological insight caused by a psychedelic experience through 14-items to be answered on a 6-point Likert scale ranging from 0 ("not at all") to 5 ("extremely").
Time frame: 10 hours after substance administration
Changes in the electrocardiogram (ECG)
Corrected QT time (QTc) will be measured twice on the study days (baseline and at peak drug effect) to examine possible drug-induced changes in the ECG as well as a safety measure (millisecond scale).
Time frame: One hour before and 2 hours after substance administration.
Adverse effects (acute and subacute)
The 2011 revised Beschwerden-Liste (B-LR) consists of a 40-item list covering a wide variety of symptoms and complaints that are answered with a four-point intensity-scoring ranging from "not at all" to "strong".
Time frame: One hour before, 10 and 24 hours after substance administration
Persisting effects of the psychedelic experiences (PEQ)
140 items are rated on a six-point scale and include attitudes about life (13 positive and 13 negative items), attitudes about self (11 positive and 11 negative items), mood changes (nine positive and nine negative items), behavioral changes (one positive and one negative item), spirituality (22 positive and 21 negative items). Three additional questions are included
Time frame: End of study (EOS) visit during EOS interview
Cognitive Tasks
Cognitive assessment will be conducted using established tasks from the CANTAB battery. The tasks are administered in a computerized format.
Time frame: 24 hours after substance administration
Peak Plasma concentration of Psilocybin and Metabolites (Cmax)
Maximal Plasma concentration of Psilocybin and Metabolites Cmax after substance administration. Calculated via blood samples.
Time frame: Right after and 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10 and 24 hours after substance administration
Time to cmax (Tmax)
Time until Psilocybin and Metabolites concentration peak in plasma after substance administration. Calculatet via blood samples after substance administration.
Time frame: Right after and 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10 and 24 hours after substance administration
Area under the concentration-time curve up to 24 h (AUC0-24)
Area under the plasma concentration versus time curve for psilocybin and metaboliteswill be calculated up to 24h using blood sampels colected during the study visits after substance administration.
Time frame: Right after and 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10 and 24 hours after substance administration
Elimination half life values (t1/2)
The elimination half life values of Psilocybin and metabolites will be calculated using blood samples collected during study visits after substance administration.
Time frame: Right after and 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10 and 24 hours after substance administration
Sleep variables of %REM
Sleep phases will be scored in every study session using an automated sleep stage classification algorithm of the SomnoArt® armband. The SomnoArt® armband will record, acceleration (3D accelerometer), and heart rate (red-infrared pulse oximeter) activity. Variables of %REM sleep is calculated as REM sleep duration divided by total sleep duration).
Time frame: 14 hours after substance administration until the end of the study day
REM Latency
Sleep phases will be scored in every study session using an automated sleep stage classification algorithm of the SomnoArt® armband. The SomnoArt® armband will record, acceleration (3D accelerometer), and heart rate (red-infrared pulse oximeter) activity. REM Latency is calculated as duration of non-REM sleep before the first REM phase.
Time frame: 14 hours after substance administration until the end of the study day
REM Efficiency
Sleep phases will be scored in every study session using an automated sleep stage classification algorithm of the SomnoArt® armband. The SomnoArt® armband will record, acceleration (3D accelerometer), and heart rate (red-infrared pulse oximeter) activity. REM Efficiency is calculated as REM sleep duration divided by the total REM episode duration
Time frame: 14 hours after substance administration until the end of the study day
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