for people ages 21-70 (full criteria)
Healthy Volunteers
healthy people welcome
study started
completion around
Principal Investigator
by Gideon St.Helen (ucsf)
Headshot of Gideon St.Helen
Gideon St.Helen



This study will examine the short-term cardiovascular (CV) effects of e-liquid pH in a randomized, crossover clinical and behavioral pharmacology study of experienced adult e-cigarette users (N=21). The specific aim of the study is to assess the impact of changes in e-liquid pH on nicotine pharmacokinetics, cardiovascular, and subjective effects of e-cigarettes.


This is a single-site, randomized, crossover study of experienced adult e-cigarette users to assess nicotine exposure, toxicant exposure, and the short-term CV effects of e-liquid pH. Three e-liquid pH conditions will be assessed on all participants: 5, 7, and 9.

Hypothesis 2a: The rate of systemic nicotine absorption is inversely related to e-liquid pH and results in lower peak blood nicotine levels at higher pH.

Hypothesis 2b: Heart rate acceleration will decrease and subjective measures of sensation in the throat, reward, and satisfaction will increase with increasing e-liquid pH.


Cardiovascular Risk Factor, Nicotine Dependence, E-Cigarettes, Vaping, E-Cig Mods, Tobacco Use Disorder, Electronic Cigarette, Remaining e-liquid pH


You can join if…

Open to people ages 21-70

  • Heart rate < 105 beats per minute (BPM)*
  • Systolic Blood pressure <160 and > 90*
  • Diastolic Blood Pressure <100 and > 50*
  • Body Mass Index (BMI) < 38.0 (at investigator's discretion for higher BMI if no other concurrent health issues)

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

  • Use e-cigarettes on at least 15 days in the past 30 for at least 3 months
  • Smoke 10 or fewer cigarettes/tobacco products per day in the last 30 days
  • Willing to use mod e-cigarette
  • Willing to abstain from tobacco product use for night before study
  • Age: > 21 years old and < 70 years old
  • Using e-liquid > 0mg/ml nicotine
  • Saliva cotinine of ≥ 30 ng/ml or NicAlert=6 (in cases where lab turn around time will delay study procedure)

You CAN'T join if...

  • Seizures
  • Cancer
  • Hepatitis B or C or Liver Disease
  • Oral Thrush
  • Heart disease
  • Glaucoma
  • Kidney disease or urinary retention
  • Diabetes
  • High Blood Pressure (taking sympatholytic medications such as alpha and beta blockers)
  • History of stroke
  • An ulcer in the past year
  • Thyroid disease (okay if controlled with medication)
  • 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 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
  • Recent onset or change in cough, fever and/or abdominal symptoms (vomiting or pain) in the past two weeks. (If yes, participant can re-screen when symptoms resolve).
  • 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)
  • Opioid replacement therapy (including methadone, buprenorphine, or other)
  • Positive urine cannabis is not exclusionary but participant must report use of cannabis and agree to abstain from cannabis use for the duration of the study
  • Psychiatric medications
  • Current regular use of any psychiatric medications with the exception of Selective Serotonin Reuptake Inhibitor (SSRI) and serotonin-norepinephrine reuptake Inhibitor (SNRIs) and current evaluation by the study physician that the participant is otherwise healthy, stable, and able to participate.
  • Medications
  • Use of medications that are inducers of nicotine metabolizing enzyme CYP2A4 (Example: rifampicin, carbamazepine, phenobarbital, and other anticonvulsant drugs).
  • Concurrent use of nicotine-containing medications
  • Any stimulant medications (example: Adderall) generally given for Attention deficit hyperactivity disorder (ADHD) treatment
  • Use of sympatholytic medications that affect cardiovascular conditions including hypertension, (Example: beta and alpha-blockers)
  • Other/Misc. Chronic Health Conditions
  • Fainting (within the last 30 days)
  • 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
  • Planning to quit vaping within the next 60 days
  • Uncomfortable with getting blood drawn


  • Zuckerberg San Francisco General Hospital accepting new patients
    San Francisco California 94110 United States
  • University of California, San Francisco accepting new patients
    San Francisco California 94143 United States

Lead Scientist at University of California Health

  • Gideon St.Helen (ucsf)
    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 21 study participants
Last Updated