How histamine affects blood flow to the lungs after exercise.
The Role of Histamines on Central Hemodynamics
This study tests whether blocking histamine changes blood flow and pressures in the lungs after exercise in healthy young adults.
Quick facts
| Phase | Not applicable |
|---|---|
| Study type | Interventional |
| Enrollment | 20 (estimated) |
| Ages | 19 Years to 39 Years |
| Sex | All |
| Sponsor | University of British Columbia Academic / other |
| Locations | 1 site (Kelowna, British Columbia) |
| Trial ID | NCT07285031 on ClinicalTrials.gov |
What this trial studies
Healthy adults will visit a lab three times to complete an exercise bout while researchers measure pulmonary blood flow and pressures using ultrasound/echocardiography. On intervention visits participants will receive either diphenhydramine (an antihistamine) or a placebo and measurements will be repeated before and after exercise. The design compares pulmonary hemodynamic responses with and without histamine blockade to see if histamine contributes to sustained post-exercise pulmonary blood flow. The study excludes people with heart, lung, or metabolic disease, smokers, those taking medications, pregnant or breastfeeding individuals, and anyone without usable tricuspid regurgitation for the primary measurement.
Who should consider this trial
Good fit: Ideal candidates are healthy adults aged 19–39 who can attend three lab visits, are non-smokers, not taking regular medications, not pregnant or breastfeeding, and have measurable tricuspid regurgitation on echocardiography.
Not a fit: People with diagnosed heart, lung (including asthma), or metabolic disease, current or recent smokers, pregnant or breastfeeding individuals, those on chronic medications, or older adults are unlikely to be eligible or benefit from the results directly.
Why it matters
Potential benefit: If successful, the findings could clarify whether histamine helps sustain increased pulmonary blood flow after exercise and inform guidance on antihistamine use and exercise physiology.
How similar studies have performed: Previous work in limb muscles showed that blocking histamine reduces post-exercise blood flow, but effects in the pulmonary circulation have not been studied before.
Eligibility criteria
Show full inclusion / exclusion criteria
Inclusion Criteria: 1. Age: 19 - 39. 2. Willing to visit the lab on 3 separate occasions. Exclusion Criteria: 1. Previously diagnosed heart condition, 2. Previously diagnosed lung condition (including asthma), 3. Previously diagnosed metabolic condition, 4. Currently smokers (cigarettes, electronic cigarettes, cannabis) or who have smoked within the last 3 months, 5. Resting blood pressure \>140/90 mmHg, 6. Unable to obtain appropriate quality ultrasound images of the heart., 7. Individuals without tricuspid regurgitation at rest to allow assessment of the primary outcome, 8. Pregnant or trying to become pregnant, 9. Breastfeeding, 10. Chronically take antihistamines (i.e. daily), 11. History of adverse reactions to antihistamines, 12. Never taken antihistamines previously, 13. Currently taking any medications (including oral contraceptives).
Where this trial is running
Kelowna, British Columbia
- University of British Columbia — Kelowna, British Columbia, Canada (Recruiting)
Study contacts
- Study coordinator: Neil Eves, PhD
- Email: neil.eves@ubc.ca
- Phone: (250) 807-9676
How to participate
- Review the eligibility criteria above with your treating physician.
- Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
- Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.