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

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.

Recruiting

Interested in participating?

Request Info

Key information

Conditions

Multi-system Atrophy - Parkinsonian Type Autonomic Nervous System Diseases Basal Ganglia Diseases Brain Diseases Cardiovascular Diseases Central Nervous System Diseases Hypotension Movement Disorders Multiple System Atrophy Nervous System Diseases Neurodegenerative Diseases Orthostatic Hypotension, Dysautonomic Parkinson Disease Parkinsonian Disorders Primary Dysautonomias Shy-Drager Syndrome Synucleinopathies Vascular Diseases

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 1 / Phase 2

Primary location

Centre Hospitalier Universitaire Vaudois, Lausanne, Canton of Vaud, Switzerland

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

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.

Treatment and study plan

Administration of Carbidopa/levodopa

Drug

Participants will perform beat-by-beat orthostatic tests (Schellong tests) before and after intake of single doses of carbidopa:levodopa combinations at 3 different ratios

Primary outcomes

Feasibility of future large-scale double-blind randomized controlled trial (RCT)

Time frame: From enrollment to the end of study at 5 weeks.
The primary objective is to investigate the feasibility of conducting a future large-scale double-blind randomized controlled trial (RCT) assessing the effect on orthostatic hypotension (OH) of different dosages of Carbidopa (20, 50 or 100 mg), for a constant Levodopa dose (200 mg) through:
- Recruitment rate: Mean number of patients informed per month during the recruitment period, % of patients wiling to participate to the study among the informed patients, % of patients eligible among the informed patients
- Adherence rate:% of patients completing the study intervention period among randomized patients
- Retention rate:% of patients showing up at the last follow-up visit among patients who have completed the study intervention period, % of drop-outs among randomized patients at last follow-up visit
- Data completion rate of the therapeutic effect measures: % of patients with analysable OH data at week 1, 2 and 3.

Study contacts

Contact information is provided by the study sponsor or research team.

Julien BALLY, Dr PD-MER

CONTACT

[email protected]

+41 79 556 78 19

Sponsors and collaborators

Lead sponsor

Julien Bally

Other

Registry information

Official study 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)

Acronym: CARBIDOH

Important dates

Study start: 2025
Primary completion: 2026
Study completion: 2026
First posted: Feb 18, 2025
Registry last updated: Jan 29, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

Published trials that share one or more normalized conditions with this study.

Recruiting