Recruiting

Histamines

Sponsor:

University of British Columbia

Code:

NCT07285031

Conditions

Histamine

Exercise

Eligibility Criteria

Sex: All

Age: 19 - 39

Healthy Volunteers: Accepted

Interventions

Diphenhydramine hydrochloride

Placebo

Exercise Bout

Study Details

Brief 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.

Conditions

Histamine

Exercise

Study ID

NCT07285031

Start date

Dec, 2025

Status verified date

Dec, 2025

Completion date

Aug, 2026

Anticipated

Primary completion date

Aug, 2026

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 19 - 39

Healthy Volunteers: Accepted

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).

Study Design

Enrollment

20 participants

Anticipated

Allocation

Randomized

Intervention Model

Crossover

Primary purpose

Basic Science

Interventions and Outcome Measures

Arms

experimental: Blockade + Exercise Bout

Participants will ingest histamine H1 receptor blockade before performing an exercise bout.

placebo comparator: Placebo + Exercise Bout

Participants will ingest a placebo before an exercise bout.

Interventions

Diphenhydramine hydrochloride

H1 receptor antagonist: 50mg Diphenhydramine Hydrochloride

Placebo

Placebo

Exercise Bout

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.

Primary outcome measure

  • Systolic pulmonary artery pressure [ Time Frame: Pre-exercise and 10, 20, and 30-minutes post-exercise. ]

Central Contacts and Locations

Central contacts

Neil Eves, PhD

(250) 807-9676neil.eves@ubc.ca

Cassidy Williams, BHK

(250) 807-9676cwilli08@student.ubc.ca

Locations

University of British Columbia

Recruiting

Kelowna, British Columbia, Canada, V1V2L2

Contacts

Neil Eves, PhD

(250) 807-9676neil.eves@ubc.ca

More Information

Sponsor

University of British Columbia

Last update posted

Dec 23, 2025

Last verified

Dec, 2025

Keywords

  • histamine
  • exercise
  • pulmonary blood flow
  • pulmonary function
  • femoral blood flow

Trial information was received from ClinicalTrials.gov and was last updated on 2026-09-10. This information was provided to ClinicalTrials.gov by University of British Columbia on 2025-12-23.