A Study Testing if Daily Tadalafil Improves Movement Symptoms in Patients with Early-Stage Parkinson’s Disease Who Have Not Yet Started Treatment

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What is this study about?

This study examines Parkinson’s disease in its early stages. Parkinson’s disease is a condition that affects the brain and causes problems with movement, such as tremors, stiffness, and slow movements. The treatment being tested is tadalafil, a medication that is taken by mouth daily. Tadalafil is already used for other medical conditions, and this study wants to see if it can help improve movement problems in people who have early-stage Parkinson’s disease and have not yet taken any medications for this condition.

The purpose of this study is to find out whether taking tadalafil every day can improve movement symptoms in people with early-stage Parkinson’s disease who have not yet needed medication for their symptoms. The study will last for two weeks, during which participants will take tadalafil daily. The maximum daily amount of the medication is 20 milligrams, and the total amount taken over the entire treatment period is 210 milligrams.

During the study, movement symptoms will be measured at the beginning and again after two weeks of taking the medication to see if there are any changes. Blood pressure and heart rate will also be checked at these times. Any side effects will be recorded, including things like headache, stomach discomfort, back pain, muscle pain, facial flushing, stuffy nose, unwanted erections, and changes in sexual desire. At the end of the two weeks, participants will be asked about their experience with the treatment and how satisfied they are with the results.

1 Initial assessment

At the start of the study, your motor symptoms (movement-related symptoms) will be assessed using a standardized rating scale called MDS-UPDRS part III. This scale evaluates how Parkinson’s disease affects your movements.

Your blood pressure will be measured in millimeters of mercury (mmHg).

Your heart rate will be measured in beats per minute (bpm).

2 Daily medication period

You will take tadalafil tablets by mouth daily for a period of two weeks.

The medication will be administered in tablet form that you swallow.

You will need to continue taking the medication every day throughout this two-week period.

3 Monitoring for side effects

During the two-week period, any adverse events (unwanted effects or health problems) will be recorded.

Specific side effects will be assessed, including: headache, dyspepsia (indigestion or stomach discomfort), back pain, muscle pain, flushing (redness or warmth in the face or body), nasal congestion (stuffy nose), unwanted erections, and changes in libido (sex drive).

4 Final assessment after two weeks

After completing the two-week treatment period, your motor symptoms will be assessed again using the same MDS-UPDRS part III scale to measure any changes.

Your blood pressure and heart rate will be measured again.

You will be asked to evaluate how burdensome the treatment was for you using a five-point scale.

You will be asked to rate your satisfaction with the outcome of the treatment using a five-point scale.

Who Can Join the Study?

You must have been diagnosed with early-stage Parkinson’s disease, which is a condition affecting movement and coordination in its beginning phase
Your daily activities should not be limited by your condition in a way that would require treatment with medications to control symptoms
You must not have taken any medications for Parkinson’s disease before
Your blood pressure must be normal, meaning it should be higher than 90/60 mm Hg and lower than 120/80 mm Hg. Blood pressure is the force of blood pushing against the walls of your arteries
You must be older than 18 years of age
You must be willing and able to give your informed consent, which means you understand the study and agree to participate voluntarily
You must be able to follow the study requirements and procedures
You must be able to understand the Dutch language

Who Cannot Join the Study?

Pregnant women or women who are breastfeeding cannot take part in this study because the medication being tested may affect the baby
People who are already taking medications for Parkinson’s disease cannot participate, as this study is only for patients who have not yet started treatment
Patients with advanced stages of Parkinson’s disease are not eligible, as the study focuses on people in the early stages of the condition
People who are currently taking nitrates, which are medications used to treat chest pain or heart problems, cannot join because they may have dangerous interactions with the study medication
Patients with severe heart disease or who have had a recent heart attack or stroke within the last six months cannot participate due to safety concerns
People with low blood pressure that is not well controlled are excluded from the study
Patients with severe kidney problems or severe liver problems cannot take part because their bodies may not process the medication properly
People who have a known allergy or serious reaction to tadalafil, which is the medication being tested, or similar medications are not eligible
Patients with certain eye conditions, such as a history of vision loss due to problems with blood flow to the eye, cannot participate
People who are unable to give their informed consent, meaning they cannot understand and agree to participate in the study, are excluded

Where you can join this trial?

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Other Sites

Site Name	City	Country	Status
Abwwxjtbs Uoc	Amsterdam	The Netherlands

Trial status

Country	Status	Recruitment Start
The Netherlands	Recruiting	01.03.2026

Trial locations

Investigated drugs:

Tadalafil

Tadalafil is a medication that is commonly used to treat erectile dysfunction and symptoms of an enlarged prostate. In this study, it is being tested to see if it can help improve movement problems in people with early-stage Parkinson’s disease. The medication works by relaxing blood vessels and increasing blood flow in the body, which researchers believe may also help with some of the motor symptoms experienced by Parkinson’s patients.

Investigated diseases:

Parkinson's disease

Parkinson’s Disease – Parkinson’s disease is a progressive disorder of the nervous system that affects movement. The disease develops gradually, often starting with a barely noticeable tremor in one hand. As the condition progresses, it commonly causes stiffness or slowing of movement. People with this disease may experience difficulties with balance and coordination. The symptoms worsen over time as the disease advances. Parkinson’s disease occurs when nerve cells in the brain that produce dopamine become impaired or die.

Trial ID:

2025-521819-39-00

Protocol code:

TAD-PD

Trial Phase:

Therapeutic exploratory (Phase II)

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A Study Testing if Daily Tadalafil Improves Movement Symptoms in Patients with Early-Stage Parkinson’s Disease Who Have Not Yet Started Treatment

What is this study about?

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