Histamines and Central Hemodynamics
The Role of Histamines on Central Hemodynamics
University of British Columbia
20 participants
Dec 1, 2025
INTERVENTIONAL
Conditions
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. 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.
Eligibility
Inclusion Criteria2
- Age: 19 - 39.
- Willing to visit the lab on 3 separate occasions.
Exclusion Criteria13
- 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.,
- 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).
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Interventions
H1 receptor antagonist: 50mg Diphenhydramine Hydrochloride
Placebo
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.
Locations(1)
View Full Details on ClinicalTrials.gov
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NCT07285031