ClinicalTrials.gov record NCT06831500

Feasibility Study Assessing the Effect of Carbidopa/Levodopa Ratio on Orthostatic Hypotension in Multiple System Atrophy - Parkinsonian Type and Parkinson Disease.

Record copied from ClinicalTrials.gov: Oct 10, 2026AI summaries generated: Sep 7, 2026

A Monocentric, Randomized, Double-blind Study to Assess the Feasibility of Conducting a Full-scale Randomized Controlled Trial (RCT) Assessing the Effect of Carbidopa/Levodopa Ratio on Orthostatic Hypotension (OH) in Multiple System Atrophy - Parkinsonian Type (MSA-P) and Parkinson Disease (PD) Patients (CARBIDOH)

StatusRecruitingThe study is currently enrolling participants. Only the study team can say whether a particular person can join.
Study typeInterventionalA study in which researchers assign participants to one or more interventions, such as a drug, procedure, device, behavioural programme or other approach, to measure their effects.
PhasePhase 1/2A study that combines safety and dose-finding (phase 1) with a first look at whether the treatment has an effect (phase 2).
SexAll
LocationSwitzerland
AI summaryWhat this study is about, in plain languageShow ▾Hide ▴

AI-written from the registry record, not the study's own wording. May contain errors or omissions. Check the registry text on this page and the original record ↗ before acting on it.

This is a small randomized, double-blind crossover study in people with MSA-P or Parkinson disease who are taking levodopa-containing drugs and have orthostatic hypotension. Participants receive single oral doses of three different carbidopa:levodopa ratios in random order and undergo standing (Schellong) tests before and after each dose. The study is primarily assessing feasibility measures needed to plan a larger trial.

What it is studying. The study tests whether and how different carbidopa doses (20 mg, 50 mg, 100 mg) given with a fixed levodopa dose (200 mg) affect orthostatic hypotension. Effects are measured using beat-by-beat standing tests (Schellong tests) before and after single oral doses given in randomized, double-blind order.

What the researchers hope to learn. To evaluate the feasibility of running a full-scale randomized controlled trial and to collect initial data on how different carbidopa dosages (20, 50, 100 mg) with 200 mg levodopa affect orthostatic hypotension. Feasibility metrics include recruitment rate, adherence, retention, and the proportion of analyzable OH data.

What this study is about

The study's own summary, as published on ClinicalTrials.gov. Underlined terms have a short explanation.

This study is aimed at patients with multi-system atrophy - parkinsonian type (P-MSA) or Parkinson's disease (PD) receiving dopaminergic drugs and suffering from orthostatic hypotension (OH). OH is a drop in blood pressure when standing, which can lead to symptoms of dizziness, lightheadedness, a black veil in front of the eyes and, when severe, can lead to fainting. HO is one of the symptoms present in AMS-P and PD. The standard treatment for parkinsonian symptoms of slowness and stiffness is the administration of antiparkinsonian drugs containing dopamine. These dopaminergic drugs always contain 1) levodopa (which is the precursor of dopamine) and 2) an enzyme inhibitor, which may be either benserazide (in the case of Madopar® and its generics) or carbidopa (in the case of Sinemet® or Stalevo® and their generics) and whose role is to potentiate the effect of levodopa. It has long been known that dopaminergic drugs aggravate HO. Through various mechanisms, this worsening of HO is linked as much to levodopa as to the enzyme inhibitor with which it is combined. However, investigators do not know the respective effects of these two molecules on HO. In this study, investigators examine how the ratio of Carbidopa to levodopa affects HO in the various assays of the dopaminergic drug under study.

Interventions being studied

Being studied in this trial does not mean the treatment or procedure is approved or available for this condition.

Drug
  • Administration of Carbidopa/levodopa

Eligibility

The criteria exactly as listed on ClinicalTrials.gov. Only the study team can say whether they apply to you.

Inclusion criteria

  • Informed consent form signed.
  • Patient over 18 years and under 80 years of age.
  • Patient with Multiple System Atrophy- Parkinsonian type (MSA-P) (confirmed by diagnostic criteria for clinically established and clinically probable multiple system atrophy (11); OR Patient with Parkinson Disease (PD) (12) presenting OH symptoms (getting at least one point at the 3 questions - n° 14, 15 and 16 - of the SCOPA-AUT scale that address orthostatic hypotension symptoms).
  • Patient currently receiving Dopamine-Replacement Therapy (i.e. Levodopa combined with Carbidopa or Benserazide).

Exclusion criteria

  • Patient unable to stand an overnight (at least 12 hours) withdrawal of their immediate-release DRT (last extended-, delayed-, or controlled-release dosage must be taken minimum 24 hours prior to the test).
  • Patient with known congestive heart failure, grades C and D, NYHA III and IV.
  • Patient with dementia (i.e. major cognitive impairment) associated to MSA-P or PD,
  • Patient with mild cognitive impairment, and unable to provide or understand informed consent, i.e. who does not have full capacity for discernment.
  • Current participation to other clinical trials.
  • Pregnant or lactating woman or willing to become pregnant.

Study description and what participation involves

The registry record has no detailed description beyond the summary above.

AI summaryWhat participation may involve, in plain languageShow ▾Hide ▴

AI-written from the registry record, not the study's own wording. May contain errors or omissions. Check the registry text on this page and the original record ↗ before acting on it.

Participants attend three study visits. At each visit they will take a single oral dose of one of three carbidopa:levodopa ratios (20/200 mg, 50/200 mg, 100/200 mg) in random order and undergo beat-by-beat orthostatic tests (Schellong tests) before and after dosing to measure blood-pressure changes. They must follow study medication instructions, including the required overnight (≥12-hour) withdrawal of immediate-release dopamine therapy and timing of extended-release doses. The study period runs to the end of study at about 5 weeks from enrollment.

How the study is structured. Interventional, randomized, double-blind, crossover design. Each participant receives single oral doses of three carbidopa:levodopa ratios at separate visits in random order. Beat-by-beat orthostatic (Schellong) tests are done before and after each dose. The main aim of this feasibility study is to measure recruitment, adherence, retention, and data completion to inform a future larger trial.

Questions you could ask

These questions are suggestions for a conversation with the study team or your own clinician, not advice.

  • The registry lists this study under Multi-system Atrophy - Parkinsonian Type; Orthostatic Hypotension, Dysautonomic; Parkinson Disease. Does it apply to my diagnosis?
  • This is an early-phase study, mainly about safety and dose. What is already known about this treatment?
  • The listed sites are in Switzerland. Is any of them reachable for me, and does the study help with travel?
  • Which of the eligibility criteria would need to be checked with tests before I could join?

More on multiple system atrophy

Clinical trials76 trials listed for multiple system atrophyEvery trial the registry lists for multiple system atrophy, with recruitment status, phase and sites, updated from ClinicalTrials.gov.See all trials →Research updatesWhat changed in multiple system atrophy researchLatest monthly update: September 2026. Includes: Tube feeding. New research summarized each month in plain language, with links to every source paper.Read the latest update →

Important dates

Study start
Jul 18, 2025
Primary completion
November 2026 (estimated)
Study completion
November 2026 (estimated)
Target enrollment
36 participants (estimated)
Last updated on registry
Jan 29, 2026
Data verified
Oct 10, 2026

Sponsor and research team

The lead sponsor funds and oversees the trial. A pharmaceutical or biotech company sponsor typically means the study is testing that company's drug or device; a hospital, university, or government agency usually indicates investigator-initiated or publicly funded research.

Lead sponsor
Julien Bally

Central study contact

If you're interested in participating, the central contact can answer general questions about the study — including eligibility requirements and how to find a recruiting site near you. Actual eligibility is determined by the site's medical team.

Participating sites (2)

Terms used on this page · explanations by MedicalUpdates.ai

standard treatment
Treatment generally considered appropriate for a condition in a particular clinical setting. It can vary by patient, place and over time. In many studies the new treatment is added to, or compared with, standard of care.
Informed consent form
The process of explaining a study, including its risks and what participation involves, so that a person can decide freely whether to take part. Consent is usually documented in writing, and a participant can choose to leave the study later.
Inclusion Criteria
The conditions a person must meet to be considered for the study, for example a confirmed diagnosis, an age range or a test result.
Exclusion Criteria
The conditions that rule a person out even if they meet the inclusion criteria, for example other illnesses, certain medicines or pregnancy.

The study record on this page is reproduced from ClinicalTrials.gov, a database of the U.S. National Library of Medicine, where it was submitted by the study sponsor. MedicalUpdates.ai does not own this content, is not affiliated with or endorsed by ClinicalTrials.gov, NIH, or the U.S. Government, and does not verify the record. Plain-language notes, the glossary and the questions above are added by this site; text in the boxes marked "AI summary" was written by an AI model and may contain errors. Registry records change over time. Check the original record for the current version and discuss eligibility or participation with a qualified healthcare professional.

← Back to clinical trials