for people ages 21 years and up (full criteria)
Healthy Volunteers
healthy people welcome
at San Francisco, California and other locations
study started
completion around
Principal Investigator
by Gideon St. Helen, PhD
Headshot of Gideon St. Helen
Gideon St. Helen



This is a randomized, crossover study enrolling experienced dual cannabis-tobacco smokers (N=18) to describe the differences in THC and toxicant exposure, examining pharmacokinetic, subjective, and cardiovascular effects from smoking and vaping dry herb cannabis. This study will also examine the differences in toxicant exposure and cardiovascular disease risk between smoking cannabis and smoking tobacco cigarettes.

Official Title

Cardiovascular Effects of Cannabis Compared to Tobacco Use


Experienced dual cannabis-tobacco smokers will participate in a within-subject crossover study with three blocks: smoked cannabis (purchased by participants from a local dispensary), dry herb cannabis vaporizer, and usual brand tobacco cigarette. Each block will consist of 2 consecutive days on an inpatient research ward. The first inpatient day of each block will comprise of two sessions: (1) The first session will be a standardized bout to compare pharmacokinetic, physiologic, and subjective effects of cannabis and tobacco use; (2) after 6 hours of abstinence, the second session will be ad libitum access to the assigned product for 2 hours to compare subjective effects (reward, satisfaction, craving reduction) and use patterns. The second inpatient day will consist of ad libitum use of the assigned product from 8:00 in the morning to midnight. An abstinence day will be added after the second day of the last block to assess exposure and effects biomarkers during a period of abstinence from cannabis (smoked/vaped) or tobacco.


THC, Cannabis, Cannabis Smoking, Cannabis Use, Unspecified, Cigarette Smoking, Tobacco Use, Nicotine Dependence, Nicotine Withdrawal, Cardiovascular Risk Factor, vape, tobacco cigarette, marijuana, smoking, Marijuana Abuse, Tobacco Use Disorder, Smoked Cannabis, Vaped Cannabis, Either of the 2 remaining products, Remaining product


You can join if…

Open to people ages 21 years and up

  • Healthy on the basis of medical history and limited physical examination, as described below:

    Heart rate < 105 beats per minute (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.

  • Current regular user of cannabis who smokes cannabis as joint or blunt at least 3 times a week for past 3 months
  • History of cannabis vaporizer use or willingness to use the vaporizer in the study
  • Current tobacco cigarette use who smokes ≥ 5 cigarettes per day
  • Saliva cotinine ≥ 50 ng/ml
  • Test positive for D-9-tetrahydrocannabinol (THC) at screening and self-report of cannabis use

You CAN'T join if...

  • Unstable medical conditions:

    Heart disease; Uncontrolled hypertension; Thyroid disease (okay if controlled with medication); Diabetes; Hepatitis B or C or Liver disease; Glaucoma; Prostatic hypertrophy

  • Psychiatric conditions:

    Current or past schizophrenia, and/or current or past bipolar disorder; Adult onset attention deficit hyperactivity disorder (ADHD); Participants with current or past depression and/or anxiety disorders will be reviewed by the study physician and considered for inclusion; History of psychiatric hospitalizations are not exclusionary, but study participation will be determined as per study physician's approval

  • Concurrent regular use of smokeless tobacco or pipes [occasional users of these products may be enrolled if they agree to abstain from their use during the period of the study]
  • 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; Psychiatric medications: current regular use of any psychiatric medications with the exception of Selective Serotonin Reuptake Inhibitors (SSRI) and serotonin-norepinephrine reuptake inhibitors (SNRI) and current evaluation by the study physician that the participant is otherwise healthy, stable, and able to participate.

  • Other/Misc. Chronic Health Conditions:

    Oral thrush; Fainting; Untreated thyroid disease; Other "life threatening illnesses" as per study physician's discretion

  • Pregnancy:

    Pregnancy (self-reported and urine pregnancy test); Breastfeeding (determined by self-report)

  • Drug/Alcohol Dependence:

    Alcohol or illicit drug dependence within the past 12 months with the exception of those who have recently completed an alcohol/drug treatment program; Positive toxicology test at the screening visit (THC & prescribed medications okay); Methadone replacement therapy

  • Concurrent participation in another clinical trial
  • Inability to communicate in English
  • History of marijuana-induced psychosis or paranoia after smoking marijuana
  • Scoring a 2 or higher on the Severity of Dependence Scale for cannabis use
  • Planning to quit smoking or vaping within the next 60 days


  • Zuckerberg San Francisco General Hospital accepting new patients
    San Francisco California 94110 United States
  • UCSF accepting new patients
    San Francisco California 94143 United States

Lead Scientist at UCSF

  • Gideon St. Helen, PhD
    I am a toxicologist who conduct clinical pharmacology studies to understand the harms or benefits of novel tobacco products and the pharmacological interaction between cannabis and tobacco when co-administered.


accepting new patients
Start Date
Completion Date
University of California, San Francisco
Study Type
Expecting 18 study participants
Last Updated