for people ages 21-65 (full criteria)
Healthy Volunteers
healthy people welcome
at San Francisco, California
study started
completion around
Principal Investigator
by Gideon St Helen



This is a crossover, randomized, double-blinded clinical pharmacology study enrolling dual cannabis-tobacco smokers to better understand the combined effects of co-administering cannabis and tobacco. The project aims to describe the pharmacokinetics and pharmacodynamics of marijuana-tobacco co-administration by delivering THC and nicotine in various combinations. This foundational study will establish a research program focused on elucidating the public health consequences of marijuana-tobacco co-use.


This is a single-center, within-subject (crossover), randomized, double-blinded clinical pharmacology study of over 8 study visits (days). Participants will be non-treatment-seeking, healthy frequent users of both marijuana and tobacco/nicotine, age 21 to 65 years (21 years because of California tobacco control law). Participants will be marijuana users of any race who smoke or vape marijuana or THC extracts at least three days a week for the past 3 months or more. The study investigators will use positive urine toxicology THC results and self-report of marijuana smoking/vaping to determine eligibility. Participants must also be current users of inhaled forms of tobacco/nicotine (cigarettes, cigars, e-cigarettes) who use the product daily over the past 3 months.

Each study day will consist of a standardized session of 5 puffs of one of 8 study conditions using a PAX-3 vaporizer (PAX Labs, Inc.). Blood will be sampled multiple times for plasma THC, nicotine, and catecholamines, questionnaires administered for sensory and subjective effects, and heart rate, skin blood flow, and skin temperature will be measured. After 6 hours of abstinence, participants will have 60 minutes of ad libitum access to the assigned study condition, during which heart rate and blood pressure will be continuously monitored, blood sampled before and after for THC, nicotine, and platelet aggregation measured, and questionnaires administered.

Studies will be conducted at the CTSI Clinical Research Services-supported research ward at Zuckerberg San Francisco General.


THC, Cannabis, Cannabis Use, Cannabis Smoking, Tobacco Use, Vaping, Marijuana, Nicotine, Vape, Marijuana Abuse, Pax Loose Leaf Vaporizer, Medium marijuana and regular cigarette, Medium marijuana and Very Low Nicotine Content cigarette, High marijuana and regular cigarette, High marijuana and Very Low Nicotine Content cigarette


You can join if…

Open to people ages 21-65

  • Heart rate < 105 BPM*
  • Systolic Blood Pressure < 160 and > 90*
  • Diastolic Blood Pressure < 100 and > 50*

    *Considered out of range if both machine and manual readings are above/below these thresholds.

  • Body Mass Index ≤ 38.0 (at investigator's discretion for higher BMI if no other concurrent health issues)
  • Current regular user of cannabis who smokes or vapes cannabis or THC extracts at least three days a week for the past 3 months or more
  • Test positive for D-9-tetrahydrocannabinol (THC) at screening and self-report of cannabis use
  • Current user of inhaled forms of tobacco/nicotine (cigarette, cigars, e-cigarettes) who use the product daily for the past 3 months or more
  • Saliva cotinine ≥ 30 ng/mL

You CAN'T join if...

  • Unstable medical conditions:
  • Hypertension if uncontrolled (meaning participant has a diagnosis, but they are not taking medication/under treatment (e.g., diet or exercise plan)
  • Drug/Alcohol Dependence
    • Alcohol or illicit drug dependence within the past 12 months (currently in treatment) with the exception of those who recently completed an alcohol/drug treatment program
    • Positive toxicology test at the screening visit (THC & prescribed medications okay)
    • Opioid replacement therapy (including methadone, buprenorphine, or other)
  • Psychiatric conditions
    • Current or past schizophrenia, and/or current or past bipolar disorder
    • Major depression, current or within the past year
    • Major personality disorder
    • Participants with current or past minor or moderate depression and/or anxiety disorders will be reviewed by the PI [study physician] and considered for inclusion
    • History of psychiatric hospitalizations are not exclusionary, but study participation will be determined as per PI's [study physician's] approval
  • Current regular use of any psychiatric medications with the exception of SSRIs and SNRIs and current evaluation by the PI that the participant is otherwise healthy, stable, and able to participate
  • Congenital or acquired immunodeficiency disorders (i.e. HIV, congenital immune deficiency syndrome, chronic diseases)
  • Other disorders (i.e. ICU, malnutrition, immunosuppressive therapy)
  • Traumatic brain injury
  • Recent onset or change (worsening) in cough, fever and/or abdominal symptoms (vomiting or pain) in the past two weeks
  • Medications
    • Use of medications that are inducers of nicotine metabolizing enzyme CYP2A6 (Example: rifampicin, dexamethasone, phenobarbital, and other anticonvulsant drugs)
    • Concurrent use of nicotine-containing medications
    • Any stimulant medications (ex. Adderall) generally given for ADHD treatment
  • Other/Misc. Chronic Health Problems
    • Oral thrush
    • Fainting
    • Other "life threatening illnesses" as per study physician's discretion
  • Pregnancy
    • Pregnancy (self-reported and urine pregnancy test)
    • Breastfeeding (determined by self-report)
  • Concurrent participation in another clinical trial
  • Inability to communicate in English
  • History of marijuana-induced psychosis or paranoia after smoking marijuana
  • Scoring a 7 or higher on the Severity of Dependence Scale (SDS) for cannabis use
  • Planning to quit smoking or vaping within the next 60 days
  • Planning to quit cannabis use within the next 60 days
  • Uncomfortable with getting blood drawn
  • Willingness to abstain from tobacco smoking and all combustible products for 13 hours before admission
  • Willingness to abstain from smoking/ingestion of cannabis 13 hours before
  • Willingness to abstain from nicotine products 13 hours before each admission


  • Zuckerberg San Francisco General Hospital
    San Francisco California 94110 United States

Lead Scientist at UCSF


not yet accepting patients
Start Date
Completion Date
University of California, San Francisco
Phase 2 research study
Study Type
Expecting 48 study participants
Last Updated