Histamines and Central Hemodynamics

NCT07285031 | Recruiting

• 1 other identifier: H25-01909
• Study Type: interventional
• Target: 20
• Locations: 1 country
• Sites: 1

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

Keywords

histamine; exercise; pulmonary blood flow; pulmonary function; femoral blood flow

Outcome Measures

Primary Outcomes (1)

• 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.

  Pre-exercise and 10, 20, and 30-minutes post-exercise.

Secondary Outcomes (4)

• Tricuspid annular plane systolic displacement

  Pre-exercise and 0, 10, 20, 30, 45, and 60 minutes post-exercise.

• Right ventricular stroke volume

  Pre-exercise and 0, 10, 20, 30, 45, and 60-minutes post-exercise.

• Femoral artery blood flow

  Pre-exercise and 0, 10, 20, 30, 45, and 60-minutes post-exercise.

• Mean arterial systemic pressure

  Pre-exercise and 0, 10, 20, 30, 45, and 60-minutes post-exercise.

Study Arms (2)

Blockade + Exercise Bout

EXPERIMENTAL

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

Drug: Diphenhydramine hydrochloride; Other: Exercise Bout

Placebo + Exercise Bout

PLACEBO COMPARATOR

Participants will ingest a placebo before an exercise bout.

Other: Placebo; Other: Exercise Bout

Interventions

Diphenhydramine hydrochloride DRUG

H1 receptor antagonist: 50mg Diphenhydramine Hydrochloride

Blockade + Exercise Bout

Placebo OTHER

Placebo

Placebo + Exercise Bout

Exercise Bout OTHER

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.

Blockade + Exercise Bout; Placebo + Exercise Bout

Eligibility Criteria

• Age: 19 Years - 39 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Age: 19 - 39.
• Willing to visit the lab on 3 separate occasions.

You may not qualify if:

• 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).

Sponsors & Collaborators

• University of British Columbia: lead

Study Sites (1)

University of British Columbia

Kelowna, British Columbia, V1V2L2, Canada

RECRUITING

MeSH Terms

Conditions

Motor Activity

Interventions

Diphenhydramine

Condition Hierarchy (Ancestors)

Behavior

Intervention Hierarchy (Ancestors)

Ethylamines; Amines; Organic Chemicals; Benzhydryl Compounds; Benzene Derivatives; Hydrocarbons, Aromatic; Hydrocarbons, Cyclic; Hydrocarbons

Central Study Contacts

Neil Eves, PhD

CONTACT

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

Cassidy Williams, BHK

CONTACT

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

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: TRIPLE
• Who Masked: PARTICIPANT, INVESTIGATOR, OUTCOMES ASSESSOR
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor

Study Record Dates

• First Submitted: December 3, 2025
• First Posted: December 16, 2025
• Study Start: December 1, 2025
• Primary Completion (Estimated): August 1, 2026
• Study Completion (Estimated): August 1, 2026
• Last Updated: December 23, 2025

Record last verified: 2025-12

Locations

CA (1)