HistamineNCT07285031
Histamines and Central Hemodynamics
A study testing Diphenhydramine hydrochloride and Exercise Bout in people with Histamine and Exercise, run by University of British Columbia at 1 site in Canada.
Trial summary
When we exercise, more blood flow goes to our muscles, challenging our blood vessels. Following exercise, blood flow remains elevated and seems to be the reason for many of the positive cardiovascular benefits that occur with exercise. Read more about this study
- Who is it for?
- Ages 19 to 39 yearsHealthy volunteers can take part
- What is being tested?
- Diphenhydramine hydrochloride and Exercise Bout
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 20 participants
- Where
- 1 siteCanada
- Study dates
- Dec 2025to Aug 2026
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 19 to 39 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Age: 19 - 39.
- Willing to visit the lab on 3 separate occasions.
Who cannot join
- Previously diagnosed heart condition,
- Previously diagnosed lung condition (including asthma),
- Previously diagnosed metabolic condition,
- Currently smokers (cigarettes, electronic cigarettes, cannabis) or who have smoked within the last 3 months,
- Resting blood pressure >140/90 mmHg,
- Unable to obtain appropriate quality ultrasound images of the heart.,
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- Individuals without tricuspid regurgitation at rest to allow assessment of the primary outcome,
- Pregnant or trying to become pregnant,
- Breastfeeding,
- Chronically take antihistamines (i.e. daily),
- History of adverse reactions to antihistamines,
- Never taken antihistamines previously,
- Currently taking any medications (including oral contraceptives).
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Canada1 site, 1 recruiting
- Recruiting
University of British Columbia
Kelowna, British Columbia, V1V2L2
Neil Eves, PhD, (250) 807-9676, neil.eves@ubc.ca
About this study
Official title: The Role of Histamines on Central Hemodynamics
When we exercise, more blood flow goes to our muscles, challenging our blood vessels. Following exercise, blood flow remains elevated and seems to be the reason for many of the positive cardiovascular benefits that occur with exercise. When the actions of histamine, a molecule primarily known for its role in allergies, are blocked, there is an attenuated blood flow response following exercise. However, this effect has never been studied in the blood vessels that supply our lungs. The purpose of this study is to examine the effects of histamines on pulmonary hemodynamics following exercise.
- Being tested
- Diphenhydramine hydrochloride, Placebo, Exercise Bout
- Keywords
- histamine, exercise, pulmonary blood flow, pulmonary function, femoral blood flow
- Medical subject headings
- Motor Activity
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Diphenhydramine hydrochlorideDrug
H1 receptor antagonist: 50mg Diphenhydramine Hydrochloride
PlaceboOther
Placebo
Exercise BoutOther
Participants will complete a total of three 5-minute high intensity exercise intervals, interspersed with 5-minute lower intensity exercise bouts (4 total), for a total of 35 minutes.
| Study group | Role | What they receive |
|---|---|---|
| Blockade + Exercise Bout | Experimental | Participants will ingest histamine H1 receptor blockade before performing an exercise bout. Receives: Drug: Diphenhydramine hydrochloride; Other: Exercise Bout |
| Placebo + Exercise Bout | Placebo comparator | Participants will ingest a placebo before an exercise bout. Receives: Other: Placebo; Other: Exercise Bout |
What is being measured
The primary outcome is the main question the study is designed to answer.
Systolic pulmonary artery pressure
The difference in systolic pulmonary artery pressure (measured as tricuspid regurgitation velocity using echocardiography) between the H1 blockade condition and the placebo condition.
Measured: Pre-exercise and 10, 20, and 30-minutes post-exercise.
Secondary outcomes (4)
Tricuspid annular plane systolic displacement
The difference in tricuspid annular plane systolic displacement between the H1 receptor blockade condition and the placebo condition.
Measured: Pre-exercise and 0, 10, 20, 30, 45, and 60 minutes post-exercise.
Right ventricular stroke volume
The difference in right ventricular stroke volume (measured using pulsed wave velocity of the right ventricular outflow tract velocity time integral) between the H1 receptor blockade condition and the placebo condition.
Measured: Pre-exercise and 0, 10, 20, 30, 45, and 60-minutes post-exercise.
Femoral artery blood flow
The difference in femoral artery blood flow between the H1 receptor blockade condition and the placebo condition.
Measured: Pre-exercise and 0, 10, 20, 30, 45, and 60-minutes post-exercise.
Mean arterial systemic pressure
The difference in mean arterial systemic pressure between the H1 receptor blockade condition and the placebo condition.
Measured: Pre-exercise and 0, 10, 20, 30, 45, and 60-minutes post-exercise.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted16 Dec 2025
- Study startDec 2025 (estimated)
- Primary completionAug 2026 (estimated)
- Study completionAug 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for HistamineStudies of the same condition, open and under way.
- More trials run by University of British ColumbiaThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Triple blind
- Who is masked
- Participant, Investigator, Outcomes assessor
- Enrolment
- 20 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of British Columbia
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Neil Eves, University of British Columbia
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07285031
- Sponsor's protocol ID
- H25-01909
- Status last verified
- Dec 2025
- First submitted
- 3 Dec 2025
- Last updated
- 23 Dec 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Study at a glance
From the registry record, last updated by the sponsor on 23 Dec 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Role of Histamines on Central Hemodynamics
- ClinicalTrials.gov ID
- NCT07285031
- Acronym / sponsor ID
- H25-01909
- Keywords
- histamine, exercise, pulmonary blood flow, pulmonary function, femoral blood flow
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 20 participants (estimated)
- Lead sponsor
- University of British ColumbiaUniversity, hospital or other
- Study start
- Dec 2025 (estimated)
- Primary completion
- Aug 2026 (estimated)
- Study completion
- Aug 2026 (estimated)
- First posted
- 16 Dec 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
When we exercise, more blood flow goes to our muscles, challenging our blood vessels. Following exercise, blood flow remains elevated and seems to be the reason for many of the positive cardiovascular benefits that occur with exercise. When the actions of histamine, a molecule primarily known for its role in allergies, are blocked, there is an attenuated blood flow response following exercise. However, this effect has never been studied in the blood vessels that supply our lungs. The purpose of this study is to examine the effects of histamines on pulmonary hemodynamics following exercise.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Triple blind (participant, investigator, outcomes assessor)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Blockade + Exercise Bout | Experimental | Drug: Diphenhydramine hydrochloride, Other: Exercise BoutParticipants will ingest histamine H1 receptor blockade before performing an exercise bout. |
| Placebo + Exercise Bout | Placebo comparator | Other: Placebo, Other: Exercise BoutParticipants will ingest a placebo before an exercise bout. |
Who may qualify
- Ages
- 19 to 39 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (2 listed)
- Age: 19 - 39.
- Willing to visit the lab on 3 separate occasions.
Key exclusion criteria (13 listed)
- Previously diagnosed heart condition,
- Previously diagnosed lung condition (including asthma),
- Previously diagnosed metabolic condition,
- Currently smokers (cigarettes, electronic cigarettes, cannabis) or who have smoked within the last 3 months,
- Resting blood pressure >140/90 mmHg,
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Diphenhydramine hydrochlorideH1 receptor antagonist: 50mg Diphenhydramine Hydrochloride | Drug | Blockade + Exercise Bout |
| PlaceboPlacebo | Other | Placebo + Exercise Bout |
| Exercise BoutParticipants will complete a total of three 5-minute high intensity exercise intervals, interspersed with 5-minute lower intensity exercise bouts (4 total), for a total of 35 minutes. | Other | Blockade + Exercise Bout, Placebo + Exercise Bout |
Primary outcome
Systolic pulmonary artery pressure
Time frame: Pre-exercise and 10, 20, and 30-minutes post-exercise.
The difference in systolic pulmonary artery pressure (measured as tricuspid regurgitation velocity using echocardiography) between the H1 blockade condition and the placebo condition.
4 secondary outcomes
Tricuspid annular plane systolic displacement
Time frame: Pre-exercise and 0, 10, 20, 30, 45, and 60 minutes post-exercise.
Right ventricular stroke volume
Time frame: Pre-exercise and 0, 10, 20, 30, 45, and 60-minutes post-exercise.
Femoral artery blood flow
Time frame: Pre-exercise and 0, 10, 20, 30, 45, and 60-minutes post-exercise.
Mean arterial systemic pressure
Time frame: Pre-exercise and 0, 10, 20, 30, 45, and 60-minutes post-exercise.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 23 Dec 2025.
- Individual participant dataSharing planned: Undecided
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Diphenhydramine hydrochloride and Exercise Bout in people with Histamine and Exercise, run by University of British Columbia at 1 site in Canada.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 2 inclusion and 13 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 23 Dec 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Canada. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Neil Eves, PhD ((250) 807-9676, neil.eves@ubc.ca), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Systolic pulmonary artery pressure (time frame: Pre-exercise and 10, 20, and 30-minutes post-exercise.). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 23 Dec 2025.