for people ages 21-70 (full criteria)
Healthy Volunteers
healthy people welcome
at San Francisco, California and other locations
study started
completion around
Principal Investigator
by Gideon St.Helen
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
  • UCSF accepting new patients
    San Francisco California 94143 United States

Lead Scientist at UCSF

  • Gideon St.Helen
    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