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Taking people in SwitzerlandPhase 1/2

Testing carbidopa and levodopa ratios for low blood pressure on standing

Tests carbidopa and levodopa dose ratios in people with Parkinson disease or MSA-P.

Key facts

Who runs it
Julien Bally
Where
Lausanne, SwitzerlandSee the 2 sites
Trial code
Registry title
Feasibility Study Assessing the Effect of Carbidopa/Levodopa Ratio on Orthostatic Hypotension in Multiple System Atrophy - Parkinsonian Type and Parkinson Disease.
Status
Recruiting
Phase
Phase 1/2
People taking part
36 people, planned
Started
18 Jul 2025
Expected to end
Nov 2026
Type of study
Interventional, 3 groupsOne group gets an existing treatment, for comparison.
Treatments tested
  • Administration of Carbidopa/levodopa
Record updated
29 January 2026

Who can take part

AI summary

From the trial's eligibility criteria. Machine-read from the registry text on this page, so it can be wrong. The registry text below and the trial team decide who can take part.

The trial is looking for adults with multiple system atrophy (parkinsonian type) or Parkinson's disease who take dopamine-replacement medicine and have a drop in blood pressure when standing.

Age
Over 18 years and under 80 years.
Sex
All sexes can join.
Disease stage
Multiple system atrophy, parkinsonian type (MSA-P), or Parkinson's disease with symptoms of orthostatic hypotension (a drop in blood pressure when standing). For Parkinson's disease, at least one point on the SCOPA-AUT questions 14, 15 and 16.
Earlier treatment
Must currently be taking dopamine-replacement therapy (levodopa with carbidopa or benserazide).

Main reasons for not taking part

  • Cannot stop immediate-release dopamine-replacement medicine for at least 12 hours overnight
  • Known congestive heart failure, NYHA grade III or IV
  • Dementia linked to MSA-P or Parkinson's disease
  • Mild cognitive impairment, unable to give or understand informed consent
  • Pregnant or breastfeeding, or planning to become pregnant

The registry criteria, word for word

Show all 10 criteriaShow less

Who can take part

  • 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)

Who cannot take part

  • 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

Where in Switzerland

  • Centre Hospitalier Universitaire VaudoisLausanne, SwitzerlandContact: Julien Bally, Dr. PD MERTaking people
  • Centre Hospitalier Universitaire Vaudois (CHUV)Lausanne, SwitzerlandContact: Matthieu Robitaille, DoctorTaking people

About the trial

What the trial wants to find out

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).

Read full original descriptionShow less

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.

The 3 groups in the trial

  • Ratio 1:10 i.e. 20 mg Carbidopa / 200 mg LevodopaExisting treatment, for comparison

    This Carbidopa / Levodopa IMP ratio will be administered as a single dose, orally, at visit 1 or 2 or 3 (random order).

    Treatment: Administration of Carbidopa/levodopa

  • Ratio 1:4 i.e. 50 mg Carbidopa / 200 mg LevodopaExisting treatment, for comparison

    This Carbidopa / Levodopa IMP ratio will be administered as a single dose, orally, at visit 1 or 2 or 3 (random order).

    Treatment: Administration of Carbidopa/levodopa

  • Ratio 1:2 i.e. 100 mg Carbidopa / 200 mg LevodopaTreatment being tested

    This Carbidopa / Levodopa IMP ratio will be administered as a single dose, orally, at visit 1 or 2 or 3 (random order).

    Treatment: Administration of Carbidopa/levodopa

Questions to ask the study team

  1. How often do I need to come in, and for how long each time?
  2. Are travel costs paid?
  3. Can I keep my own doctor?
  4. What happens if I want to stop?

Contact the study team: see the registry record → Contacts and Locations

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Data and sources

Registry record
Listed on ClinicalTrials.gov.
Official title
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)
Plain-language title
Testing carbidopa and levodopa ratios for low blood pressure on standingGenerated from the registry record. The registry title is the official one.
AI summary
From the trial's eligibility criteria. Read by machine on 12 November 2026.
Record updated
29 January 2026