A Phase 2/3 interventional study of Dextrose and Sildenafil 20mg in Pulmonary Arterial Hypertension (PAH) (WHO Group 1 PH), sponsored by Silvia Ulrich. Recruiting at 1 site in Switzerland. Open to participants aged 18 Years to 80 Years. Per ClinicalTrials.gov, last updated 2026-11-04.
Sponsored by Silvia Ulrich · Phase 2/3, Interventional, and Treatment
The goal of this clinical study is to investigate whether the additional intake of sildenafil 20mg on top of standard medical treatment results in a benefit on maximum exercise workload (Wmax) in patients with pulmonary arterial hypertension (PAH).
This study is a prospective, randomized, cross-over trial evaluating the effects of additive 20 mg sildenafil versus placebo/sham dextrose candy on exercise capacity in patients with previously diagnosed pulmonary arterial hypertension (PAH).
PAH is a progressive and debilitating disease characterized by increased mean pulmonary arterial pressure (mPAP) and pulmonary vascular resistance (PVR), leading to right ventricular overload, and ultimately right heart failure. Despite advancements in pharmacological therapy, treatment options remain limited and optimizing individualized approaches to improve exercise capacity and manage symptom burden remains a challenge.
Phosphodiesterase type 5 inhibitors, such as sildenafil, are cornerstones of PAH treatment, enhancing pulmonary vasodilation and improving haemodynamics. While three times daily dosing is standard with three time 20-80mg daily. On-demand additive sildenafil use before exercise has not been studied, but as recent trials have shown that dosing up to three times 80mg is as safe as 20mg, there is a potential that additive therapy may be beneficial. Given sildenafil's rapid onset of action with peak effects after 30-120 minutes, it may offer acute functional benefits regarding maximum workload (Wmax) when administered shortly beforehand, in the terms of a "pill-in-the pocket" intake.
After providing informed consent, eligible participants (aged 18 - 80 years, with PAH diagnosed according to the ESC/ERS 2022/2019 guidelines) will be randomly assigned to receive either 20 mg sildenafil or dextrose candy (Dextro Energy). 45 minutes post-intake, they will undergo incremental spiroergometry (10-20 W increases) and right heart focused stress-echocardiography on a cycle ergometer until exhaustion. After a rest phase of 30 minutes, patients will perform CWRET at 75% of achieved Wmax until exhaustion. Then, after a washout period of minimum 24 hours up to 12 weeks, participants will cross over to the opposite treatment, repeating the same protocol.
In case of a beneficial result, our study could support the use of an additive pill-in-the-pocket therapy strategy which may allow treatment to be tailored to the individual activity demands of patients.
699 studies on the registry are indexed under Pulmonary Arterial Hypertension; 140 are open to participants now.
This study's planned enrollment of 20 is below the median of 40 across 477 interventional studies indexed under Pulmonary Arterial Hypertension.
Browse Pulmonary Arterial Hypertension studies →This is the only study on the registry with Silvia Ulrich as lead sponsor.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Concurrent medication with:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
From a breathing test (spirometry): how much air you can blow out in the first second. Often given as a percentage of what is expected for your age, height and sex.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
CYP3A is a group of enzymes, mainly CYP3A4, in the liver and gut that break down many medicines. Some medicines, supplements and foods (grapefruit, St John’s wort) slow them down or speed them up, which changes how much of a study drug stays in the body.
Studies list them so they can be avoided or switched; bring a list of everything you take, including supplements.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
FEV1
From a breathing test (spirometry): how much air you can blow out in the first second. Often given as a percentage of what is expected for your age, height and sex.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
CYP3A (CYP3A4) inhibitors and inducers
CYP3A is a group of enzymes, mainly CYP3A4, in the liver and gut that break down many medicines. Some medicines, supplements and foods (grapefruit, St John’s wort) slow them down or speed them up, which changes how much of a study drug stays in the body.
Studies list them so they can be avoided or switched; bring a list of everything you take, including supplements.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Group A will receive the active comparator first (Sildenafil 20mg) in accordance with the Cross-Over trial design.
Drug: Dextrose · Drug: Sildenafil 20mg
Group B will receive the placebo comparator first (Dextrose Candy) in accordance with the Cross-Over trial design.
Drug: Dextrose · Drug: Sildenafil 20mg
Administration of Dextrose Candy by mouth as a tablet.
Also known as: Dextro Energy, Dextrose Candy
Administration of Sildenafil 20mg by mouth as a tablet.
Also known as: Revatio 20mg
Maximum workload (Wmax)
The difference in maximum workload (Wmax) attained during maximum spiroergometry 45 minutes after treatment with Sildenafil 20mg (Revatio 20mg) versus dextrose candy (Dextro Energy).
Time frame: Within 1 - 90 days
Time to Exhaustion (Tmax)
Difference in Time to Exhaustion (Tmax)attained during CWRET after treatment with Sildenafil 20mg (Revatio 20mg) versus dextrose candy (Dextro Energy)
Time frame: Within 1 - 90 days
Cardiometabolic parameters (CPET, CWRET): Oxygen Saturation (SpO2)
Change in Oxygen Saturation (SpO2) during CPET / CWRET
Time frame: Within 1 - 90 days
Focused Stress-Echocardiography (Right Heart): Stroke Volume (SV)
Change in Stroke Volume (SV) during CPET
Time frame: Within 1 - 90 days
Arterial blood gases: Arterial Partial Pressure of Oxygen (PaO2)
Change in Arterial Partial Pressure of Oxygen (PaO2) during CPET.
Time frame: Within 1 - 90 days
Borg CR10 (Borg Category-Ratio 10 Scale)
Changes in Borg CR10 questionnaire (Borg Category-Ratio 10 Scale) after CPET / CWRET (0-10, higher values indicate more severe symptoms)
Time frame: Within 1 - 90 days
Focused Stress-Echocardiography (Right Heart): Tricuspid Regurgitation Pressure Gradient (TRPG)
Change in Tricuspid Regurgitation Pressure Gradient (TRPG) during CPET
Time frame: Within 1 - 90 days
Cardiometabolic parameters (CPET / CWRET): Blood Pressure (BP)
Change in Blood Pressure (BP) during CPET / CWRET
Time frame: Within 1 - 90 days
Cardiometabolic parameters (CPET / CWRET): Heart Rate (HR)
Change in Heart Rate (HR) during CPET / CWRET
Time frame: Within 1 - 90 days
Cardiometabolic parameters (CPET / CWRET): Rate Pressure Product (RPP)
Change in Rate Pressure Product (RPP) during CPET / CWRET
Time frame: Within 1 - 90 days
Cardiometabolic parameters (CPET / CWRET): Maximum Uptake of Oxygen (V'O2max)
Change Maximum Uptake of Oxygen (V'O2max) during CPET / CWRET
Time frame: Within 1 - 90 days
Cardiometabolic parameters (CPET / CWRET): Maximum Carbon Dioxide Production (V'CO2max)
Change in Maximum Carbon Dioxide Production (V'CO2max) during CPET / CWRET
Time frame: Within 1 - 90 days
Cardiometabolic parameters (CPET / CWRET): Maximum Minute Ventilation (V'Emax)
Change in Maximum Minute Ventilation (V'Emax) during CPET / CWRET
Time frame: Within 1 - 90 days
Cardiometabolic parameters (CPET / CWRET): Maximum Ventilatory Equivalent for Oxygen (V'E/VO2)
Change in Maximum Ventilatory Equivalent for Oxygen (V'E/VO2) during CPET / CWRET
Time frame: Within 1 - 90 days
Cardiometabolic parameters (CPET / CWRET): Maximum Ventilatory Equivalent for Carbon Dioxide (V'E/VCO2)
Change in Maximum Ventilatory Equivalent for Carbon Dioxide (V'E/VCO2) during CPET / CWRET
Time frame: Within 1 - 90 days
Cardiometabolic parameters (CPET / CWRET): Breathing Frequency (BF)
Change in Breathing Frequency (BF) during CPET / CWRET
Time frame: Within 1 - 90 days
Cardiometabolic parameters (CPET / CWRET): Breathing Reserve (BR)
Change in Breathing Reserve (BR) during CPET / CWRET
Time frame: Within 1 - 90 days
Arterial blood gases: Arterial Partial Pressure of Carbon Dioxide (PaCO2)
Change in Arterial Partial Pressure of Carbon Dioxide (PaCO2) during CPET.
Time frame: Within 1 - 90 days
Arterial blood gases: Bicarbonate (HCO3-)
Change in Bicarbonate HCO3- before and after CPET.
Time frame: Within 1 - 90 days
Arterial blood gases: Arterial Oxygen Saturation (SaO2)
Change in Arterial Oxygen Saturation (SaO2) before and after CPET.
Time frame: Within 1 - 90 days
Arterial blood gases: Base Excess (BE)
Change in Base Excess (BE) before and after CPET.
Time frame: Within 1 - 90 days
Arterial blood gases: Lactate (lac)
Change in Lactate (lac) concentration before and after CPET.
Time frame: Within 1 - 90 days
Arterial blood gases: Hemoglobin (Hb)
Change in Hemoglobin (Hb) before and after CPET.
Time frame: Within 1 - 90 days
Arterial blood gases: Hematocrit (Hct)
Change in Hematocrit (Hct) before and after CPET.
Time frame: Within 1 - 90 days
Focused Stress-Echocardiography (Right Heart): Tricuspid Regurgitation Velocity (TRV)
Change in Tricuspid Regurgitation Velocity (TRV) during CPET
Time frame: Within 1 - 90 days
Focused Stress-Echocardiography (Right Heart): Right Atrial Pressure (RAP)
Change in Right Atrial Pressure (RAP) during CPET
Time frame: Within 1 - 90 days
Focused Stress-Echocardiography (Right Heart): Systolic Pulmonary Arterial Pressure (sPAP)
Change in Systolic Pulmonary Arterial Pressure (sPAP) during CPET
Time frame: Within 1 - 90 days
Focused Stress-Echocardiography (Right Heart): Fractional Area Change (FAC)
Change in Fractional Area Change (FAC) during CPET
Time frame: Within 1 - 90 days
Focused Stress-Echocardiography (Right Heart): Tricuspid Annular Plane Systolic Excursion (TAPSE)
Change in Tricuspid Annular Plane Systolic Excursion (TAPSE) during CPET
Time frame: Within 1 - 90 days
Focused Stress-Echocardiography (Right Heart): Ratio of Tricuspid Regurgitation Pressure Gradient to Cardiac Output (TRPG/CO)
Change in Ratio of Tricuspid Regurgitation Pressure Gradient to Cardiac Output (TRPG/CO) during CPET
Time frame: Within 1 - 90 days
Focused Stress-Echocardiography (Right Heart): Cardiac Output (CO)
Change in Cardiac Output (CO) during CPET
Time frame: Within 1 - 90 days
Focused Stress-Echocardiography (Right Heart): Pulmonary Vascular Resistance (PVR)
Change in Pulmonary Vascular Resistance (PVR) during CPET
Time frame: Within 1 - 90 days
Safety Profile / (S)AEs
Safety and (S)AEs of each Intervention \[sildenafil 20mg (Revatio 20mg) and dextrose candy (Dextro Energy)\] will be assessed.
Time frame: (S)AEs will be assessed immediately after each intervention (A or B) during the corresponding study visits (1 and 2).
PDFs hosted by the registry, ClinicalTrials.gov.
Plan to share: No — Access to anonymised IPD that underlie results in a publication will be considered individually upon reasonable request.
Started Oct 2026 (actual). Primary completion is estimated for Apr 2028, 18 months after the start.
Start moved once since we started tracking on Sep 25, 2026: Sep 2026 → Oct 2026, on Nov 4, 2026.
Earlier changes are on the record history on ClinicalTrials.gov ↗
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
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Studies of the drugs tested here: Glucose · Sildenafil
Pulmonary Arterial Hypertension →