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Psilocybin-assisted Therapy for Phantom Limb Pain

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Know the risks and potential benefits of clinical studies and talk to your health care provider before participating. Read our disclaimer for details. Identifier: NCT05224336
Recruitment Status : Recruiting
First Posted : February 4, 2022
Last Update Posted : October 6, 2023
Information provided by (Responsible Party):
Fadel Zeidan, University of California, San Diego

Brief Summary:
This double-blind placebo-controlled pilot study seeks to investigate whether psilocybin can be safely administered to people with chronic phantom limb pain (PLP) in a supportive setting with close follow-up, and its effects on pain symptoms and other moods, attitudes, and behaviors. The investigators' primary hypotheses are that psilocybin is safe to administer in people with PLP and that it will reduce scores on measures of pain. The investigators will also assess a number of secondary measures related to the behavioral and neural responses to pain after psilocybin treatment.

Condition or disease Intervention/treatment Phase
Phantom Limb Pain Drug: Psilocybin Drug: Placebo Niacin Phase 1

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Study Type : Interventional  (Clinical Trial)
Estimated Enrollment : 20 participants
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Masking Description: Participants and outcome assessor will not be made aware if participants are receiving psilocybin or placebo niacin.
Primary Purpose: Treatment
Official Title: Behavioral and Neural Mechanisms Supporting Psilocybin-assisted Therapy for Phantom Limb Pain
Actual Study Start Date : January 1, 2022
Estimated Primary Completion Date : June 1, 2024
Estimated Study Completion Date : June 1, 2024

Resource links provided by the National Library of Medicine

Arm Intervention/treatment
Experimental: Psilocybin
Participants will receive 25mg oral psilocybin one day to two weeks after baseline psychophysical and fMRI testing. Psychophysical and fMRI testing will then be employed one day to two weeks after drug administration.
Drug: Psilocybin
25mg oral psilocybin

Placebo Comparator: Niacin
Participants will receive 100mg oral niacin one day to two weeks after baseline psychophysical and fMRI testing. Psychophysical and fMRI testing will then be employed one day to two weeks after drug administration.
Drug: Placebo Niacin
100mg oral niacin

Primary Outcome Measures :
  1. Changes in Phantom Limb Pain Intensity [ Time Frame: Baseline to Post-Intervention Session (within 2 weeks after session) ]
    A validated visual analogue scale will be used to quantify the intensity and unpleasantness ratings of phantom limb pain. The minimum rating will be represented as "no pain sensation" or "not at all unpleasant," whereas the maximum was designated with "most intense imaginable" or "most unpleasant imaginable." Higher numbers correspond to higher pain.

Secondary Outcome Measures :
  1. Change in Visual Analog Scale Pain ratings [ Time Frame: Baseline to Post-Intervention Session (within 2 weeks after session) ]
    Pain ratings will be assessed in response to the noxious heat stimulation. Pain intensity and unpleasantness ratings will be assessed with a validated visual analog scale. The minimum rating ("0") is labeled as "no pain sensation" or "not at all unpleasant," whereas the maximum ("10") is labeled as "most intense imaginable" or "most unpleasant imaginable." Higher numbers correspond to higher pain.

  2. Cerebral Blood Flow (CBF) [ Time Frame: Baseline to Post-Intervention Session (within 2 weeks after session) ]
    Changes in CBF during rest, after intervention session, and during noxious heat stimulation.

  3. Brief Pain Inventory [ Time Frame: Baseline to Post-Intervention Session (within 2 weeks after session) ]
    This is a 7-item self-report measure of pain interference with general activity, mood, walking ability, work, relationships with others, sleep, and enjoyment of life.

Information from the National Library of Medicine

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the contacts provided below. For general information, Learn About Clinical Studies.

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Ages Eligible for Study:   18 Years to 75 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • Between 18 and 75 years of age
  • Amputation of one extremity
  • Experience phantom limb pain of at least one month's duration and intensity of at least 3 out of 10 on the VAS
  • Able to fluently communicate in English
  • Agree to sign the consent and HIPPA authorization
  • Willing to refrain from taking serotonergic antidepressant medication during the study period
  • Willing to refrain from using any non-prescribed psychoactive drugs, including alcohol, within 24 hours before and after study drug administration
  • Agree not to use any nonprescription medications, herbal medications, or supplements during the week prior to each drug session unless an exception is approved by the study investigators
  • Willing to refrain from smoking or use of nicotine during the period from 8:00 am on the morning of the drug sessions until they are discharged to go home at the end of the end of the session
  • Able to remain in an MRI machine without sedation
  • Women of childbearing potential must agree to practice an effective means of birth control throughout the study, from screening to the final visit
  • Have a relative or friend who can provide/accompany transportation after the drug session
  • If pain is currently being treated with analgesic medications, the analgesic regimen must be stable for at least 2 weeks prior to enrollment, and the participant must agree not to change their use of analgesic medication without first consulting with the study investigators [permissible analgesic medications are as follows: aspirin, acetaminophen, celecoxib, diflunisal, etodolac, fenoprofen, flubiprofen, gabapentin, ibuprofen, indomethacin, ketoprofen, ketorolac, mefenamic acid, meloxicam, nalbumetone, naproxen, pregabalin, proxicam, sulindac, tolmetin, and valdecoxib. PRN use of OTC analgesic medications by participants is also permissible]
  • Participants who are taking other medications acting as serotonin antagonists (e.g., cyclobenzaprine, odansetron), dopamine antagonists (e.g., metoclopramide, promethazine, prochlorperazine), dopamine agonists (e.g., levodopa, pramipexole, apomorphine), psychostimulants (e.g., modafinil, armodafinil, solriamfetol, methylphenidate, dexmethylphenidate, atomoxetine, dextroamphetamine, mixed amphetamine salts, lisdexamphetamine), anticholinergics (e.g., benzotropine, trihexyphenidyl, scopolamine, hypscyamine), or N-methyl-D-aspartate receptor antagonists (e.g., amantadine, memantine, ketamine) must be willing to discontinue those medications 1 week prior to each drug session

Exclusion Criteria:

  • Under the age of 18 or over the age of 75
  • Pregnant or nursing females
  • Females of childbearing age who are sexually active but not using birth control
  • Phantom limb pain intensity <3 out of 10 on the VAS
  • Presence of another type of chronic pain that cannot be differentiated from phantom limb pain by the participant
  • Amputation of more than one extremity
  • MRI related contraindications including pacemakers, metal implants, spinal cord stimulators etc.
  • Meet DSM-V criteria for bipolar disorder, schizophrenia, or other psychotic disorder
  • Have a first-degree relative (parent or full-sibling) with a history of bipolar disorder, schizophrenia, or other psychotic disorder
  • Judged to present a suicide risk
  • Not able to complete an MRI scan
  • Active substance use disorder (excluding tobacco and caffeine)
  • Subjects prescribed methadone or buprenorphine for any indication
  • Require concomitant treatment with efavirenz
  • Participants who are prescribed antidepressants or antipsychotics for an axis I diagnosis
  • Participants who are taking a serotonergic dietary supplement (e.g., 5-hydroxytryptophan, St. John's wort, SAM-e)
  • Participants with any neurological conditions resulting in altered perception or cognition (e.g., dementia, traumatic brain injury, mild cognitive impairment) [with the exception of phantom limb syndrome and its sequelae (depression or anxiety)]
  • Participants with a positive urine drug screen for amphetamines, barbiturates, buprenorphine, cocaine, methamphetamine, MDMA, methadone, opiates (morphine, oxycodone), or phencyclidine (PCP)
  • Have used psilocybin, psilocybin-containing mushrooms, or another serotonergic hallucinogen (e.g., LSD, mescaline, ayahuasca) for recreational purposes within the last 12 months
  • Require concomitant treatment with anti-psychotic medications (aripiprazole, asenapine, brexpiprazole, cariprazine, chlorpromazine, clozapine, fluphenazine, haloperidol, iloperidone, loxapine, mesoridazine, molindone, olanzapine, paliperidone, perphenazine, pimavanserin, pimozide, prochlorpromazine, quetiapine, risperidone, thioridazine, thiothixene, trifluperazine, or ziprasidone)
  • Require concomitant treatment with an antidepressant medication or other medications that act as MAO inhibitors or serotonin reuptake inhibitors (amitriptyline, amoxapine, bupropion, citalopram, clomipramine, desipramine, doxepin, duloxetine, escitalopram, fluoxetine, fluvoxamine, imipramine, isocarboxazid, levomilnacipram, maprotiline, milnacipram, mirtazapine, nefazodone, nortriptyline, paroxetine, phenelzine, protriptyline, selegiline, sertraline, tramadol, tranylcypromine, trazodone, trimipramine, venlafaxine, vilazodone, vortioxetine) [trazodone ≤50mg/24hr for insomnia is allowed, but not within 48hr of the psilocybin session]
  • Require concomitant treatment with medications known to inhibit UGT1A9 and UGT1A10 (e.g., diclofenac, probenecid, valproic acid)
  • Severe hearing or visual impairment
  • History of seizure disorder or epilepsy
  • History of migraine or other severe recurring headaches necessitating treatment by a neurologist or headache specialist
  • History of adverse reactions or intolerance to niacin or the rescue medications used in the study (benzodiazepines, antipsychotics, labetalol, nitroglycerin)
  • Presence of uncontrolled cardiovascular disease or uncontrolled hypertension (SBP > 140 mmHg or DBP > 90 mmHg)
  • Require concomitant treatment with an antihypertensive medication
  • QTc prolongation (QTc > 0.045 for man, QTc > 0.047 for women)
  • Subjects with history of stroke, angina, clinically significant ECG abnormality (e.g. atrial fibrillation), or artificial heart valve
  • Participants with severe renal impairment (GFR < 30 mL/min/1.73 m2)
  • Participants with any clinically significant lab abnormalities as determined by a physician on the study team
  • Myocardial infarction within the last 12 months
  • Participants who meet criteria for Child-Pugh class B or higher
  • Participants who are prescribed opioid medications
  • Participants taking other medications that may be associated with serotonin syndrome: carbamazepine, dextromethorphan, lithium, linezolid, buspirone
  • Evidence of severely compromised hepatic function

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT05224336

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Contact: Dwayne Mosbey, BA (619) 432-5278‬‬
Contact: Jon G Dean, PhD (619) 432-5278

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United States, California
University of California, San Diego Recruiting
San Diego, California, United States, 92093
Contact: Fadel Zeidan, PhD    858-246-2391   
Contact: Jon Dean, PhD    858-246-2391   
Sponsors and Collaborators
University of California, San Diego
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Responsible Party: Fadel Zeidan, Associate Professor, University of California, San Diego Identifier: NCT05224336    
Other Study ID Numbers: 200626
First Posted: February 4, 2022    Key Record Dates
Last Update Posted: October 6, 2023
Last Verified: October 2023

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Studies a U.S. FDA-regulated Drug Product: Yes
Studies a U.S. FDA-regulated Device Product: No
Keywords provided by Fadel Zeidan, University of California, San Diego:
Phantom Limb Pain
Psychedelic Therapy
Chronic Pain
Physiological Effects of Drugs
Psychotropic Drugs
Additional relevant MeSH terms:
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Phantom Limb
Perceptual Disorders
Neurobehavioral Manifestations
Neurologic Manifestations
Nervous System Diseases
Pain, Postoperative
Postoperative Complications
Pathologic Processes
Hypolipidemic Agents
Molecular Mechanisms of Pharmacological Action
Lipid Regulating Agents
Vasodilator Agents
Vitamin B Complex
Physiological Effects of Drugs
Psychotropic Drugs