for people ages 21-70 (full criteria)
Healthy Volunteers
healthy people welcome
at San Francisco, California and other locations
study started
estimated completion
Principal Investigator
by Neal Benowitz, MD
Headshot of Neal Benowitz
Neal Benowitz



This study will examine the effects of electronic cigarette e-liquid nicotine content in a randomized, crossover clinical and behavioral pharmacology study of experienced adult e-cigarette users (N=36). The specific aim is to determine the impact of nicotine content of e-liquid on nicotine pharmacology, systemic exposure to toxic volatile organic compounds, and short-term cardiovascular effects.


This is a within-subjects, crossover design of advanced electronic cigarette users in which we will examine nicotine pharmacokinetics, subjective effects, daily nicotine intake and nicotine titration, short-term cardiovascular effects, and toxicant exposure when participants are using low vs. high nicotine e-liquids.

Hypothesis 1: E-cigarette users will titrate their intake of nicotine such that they will inhale fewer aerosol toxicants and suffer less harm to health when using higher vs. lower nicotine content e-liquids.

Hypothesis 2: Compared to low nicotine, high nicotine e-liquid use will have similar cardiovascular effects throughout the day (due to compensatory behavioral changes), with similar effects on heart rate, blood pressure, and catecholamine release.

Hypothesis 3: Exposure to volatile organic compounds (VOCs) will be lower when vaping high nicotine e-liquids compared to low nicotine e-liquids.


Cardiovascular Risk Factor, Nicotine Dependence, E-Cigarettes, Vaping, E-Cig Mods, E-Liquid, Tobacco Use Disorder, Nicotine, Low Nicotine E-Liquid, Medium or High Nicotine E-Liquid, Low Nicotine


You can join if…

Open to people ages 21-70

  • 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.

  • Age: >= 21 years
  • Age: <= 70 years
  • Current regular user of open tank electronic cigarette (EC) (at least 20 times in the past 30 days) with e-liquid nicotine of 3-6 mg/mL.
  • Non-smoker or non-daily cigarette smokers agreeing to abstain from cigarettes for the duration of the study.
  • Saliva cotinine >50 ng/mL and/or NicAlert=6
  • Carbon monoxide >= 5 ppm or per discretion of Principal Investigator

You CAN'T join if...

  • Medical
  • Heart disease
  • Seizures
  • Cancer
  • Thyroid disease (okay if controlled with medication)
  • Diabetes
  • Hepatitis B or C or Liver disease
  • Glaucoma
  • Kidney disease or urinary retention
  • History of stroke
  • An ulcer in the past year
  • Active use of an inhaler for Asthma or Chronic obstructive pulmonary disease (COPD)
  • 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 and considered for inclusion
  • History of psychiatric hospitalizations is not exclusionary, but study participation will be determined as per PI's approval
  • 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 for illicit drugs at the screening visit (THC & prescribed medications okay)
  • Opioid replacement therapy (including methadone, buprenorphine, or other)
  • Psychiatric medications
  • Current regular use of any psychiatric medications with the exception of Selective Serotonin Reuptake Inhibitors (SSRIs) and serotonin-norepinephrine reuptake Inhibitors (SNRIs) and current evaluation by the PI that the participant is otherwise healthy, stable, and able to participate.
  • Medications
  • Use of medications that are inducers of nicotine metabolizing enzyme CYP2A6 (Example: rifampicin, carbamazepine, phenobarbital, and other anticonvulsant drugs).
  • Use of sympatholytic medications for cardiovascular conditions including hypertension (Example: beta and alpha-blockers)
  • Concurrent use of nicotine-containing medications
  • Any stimulant medications (example: Adderall) generally given for attention deficit hyperactivity disorder (ADHD) treatment
  • Other/Misc. Chronic Health Conditions
  • Oral thrush
  • Fainting (within the last 30 days)
  • Other "life threatening illnesses" as per PI's discretion
  • Pregnancy
  • Pregnancy (self-reported and urine pregnancy test)
  • Breastfeeding (determined by self-report)
  • Concurrent participation in another clinical trial
  • Inability to read and write in English
  • Planning to quit vaping within the next 60 days
  • Concurrent regular use of marijuana (occasional users of these products may be enrolled if they agree to abstain from their use during the period of the study)
  • Use of other tobacco products, smokeless tobacco, pipes, cigars/cigarillos, blunts/spliffs (no more than 10 times in the past month and must agree to abstain from their use during the period of the study)


  • University of California, San Francisco
    San Francisco California 94110 United States
  • Zuckerberg San Francisco General Hospital
    San Francisco California 94110 United States

Lead Scientist at UCSF

  • Neal Benowitz, MD
    Neal Benowitz has been involved in patient care and conducting research at SFGH since 1973. His research focus is on the human pharmacology of nicotine in relation to pathogenesis of and individual differences in vulnerability to tobacco-related disease, and the use of pharmacologic data as a basis for public health policies to prevent and reduce such disease.


not yet accepting patients
Start Date
Completion Date
University of California, San Francisco
Study Type
Expecting 36 study participants
Last Updated