NCT04985929

The Impact of Sildenafil on the Pulmonary Circulation in Healthy Trained and Untrained Humans

Completed Phase 2 Last updated 19 September 2024

What this trial tests

Phase 2 trial testing Sildenafil 50 mg in Healthy in 26 participants. Completed in 5 July 2024.

Timeline

1 July 2021

Primary endpoint
5 July 2024

5 July 2024

Quick facts

Lead sponsor	University of Alberta
Phase	Phase 2
Status	Completed
Study type	INTERVENTIONAL
Allocation	randomized
Design	crossover
Masking	triple
Primary purpose	basic science
Enrollment	26
Start date	1 July 2021
Primary completion	5 July 2024
Estimated completion	5 July 2024
Sites	1 location across Canada

Drugs / interventions tested

• Sildenafil 50 mg
• Placebo

Conditions studied

• Healthy — all drugs for Healthy →

Sponsor

University of Alberta

Who can join

Adults 18 to 40, any sex, with Healthy. Patients with the condition only — healthy volunteers not accepted.

Sponsor's own description

There is emerging evidence suggesting that the pulmonary vasculature and right heart may play a role in the limitation of exercise capacity in healthy individuals. It is well established that aerobic training improves cardiovascular function. While the pulmonary system is integral to the function of the cardiopulmonary system, it has been traditionally accepted that lung function does not respond to exercise training. However, recent research suggests pulmonary vascular function adaptations may occur with aerobic training, and this may contribute to enhanced exercise tolerance. Research has highlighted that increased capillary blood volume (Vc) and diffusion capacity for carbon monoxide (DLCO) are correlated with higher cardiorespiratory fitness at rest. Additionally, endurance trained participants have increased exercise DLCO concomitant to higher resting Vc when compared to untrained participants, and during exercise this difference seems to be driven by higher membrane diffusing capacity (Dm), independent of Vc or VA (alveolar volume). Of importance is also the evidence that highlights endurance trained participants having reduced pulmonary arterial pressures at rest and during exercise. Reduced pulmonary arterial pressure in endurance trained participants despite endurance trained participants consistently displaying increased diffusion capacity/pulmonary perfusion at rest and during exercise suggests a lower threshold pressure for pulmonary capillary recruitment. Together, this cross-sectional evidence suggests improvements in the pulmonary circulation due to exercise training in order to facilitate gas exchange. Whether this apparent improvement in pulmonary circulation is due to enhanced pulmonary vascular function via NO mediated vasodilation must be determined experimentally. If sildenafil administration improves DLCO, Vc, and Dm, this would provide evidence that the NO mediated vasodilatory pathway plays a role in the regulation of vascular tone, function, and perfusion across the pulmonary vasculature. Should a larger response to sildenafil be observed in untrained persons, this would suggest better baseline vascular function in trained participants compared to untrained. This would provide strong evidence that aerobic training improves pulmonary vasculature function which is contrary to the conventional understanding of aerobic training on the cardiopulmonary system.

Publications & conference data

No peer-reviewed publications indexed yet for this trial. Completed trials usually publish results within 12-18 months.