Skip to content
Clinical Trials – home

Rare diseases

Investigational molecules

Locations

Our offerNewsroom

Not yet recruiting

Effect of botulinum toxin type A - haemagglutinin complex on refractory upper‑limb resting tremor in Parkinson disease patients (drug‑combination study)

Verified siteRegistered drugNo placebo
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

What is this trial about?

A plain-language summary of the goals, design and what participants do

The study focuses on people with Parkinson disease who continue to have a shaking of the hand or arm that does not improve with usual medicines. The treatment being tested is an injection of botulinum toxin, compared with an injection of placebo. The aim is to find out whether the toxin can lower the intensity of the rest tremor in the affected arm.

Participants will receive a single injection in the arm that has the tremor. After a set period of about six weeks, they will be asked to complete questionnaires about how they feel and how the tremor has changed. In a crossover design, each participant will later receive the other injection (toxin or placebo) so that both treatments are evaluated in the same person. Throughout the study, any side effects or new problems will be recorded, and the strength of the hand will be measured with a simple hand‑grip test.

The research process

The trial runs in 8 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Baseline assessment

    You attend the first study visit after joining the trial. during this visit, the research team records your current tremor level, quality of life, and daily activity scores using standard questionnaires. these measurements serve as the reference point for later comparisons.

  2. Step 2

    Randomized injection (first period)

    You are assigned to receive either the active medication or a placebo. the active medication is Dysport, an injectable form of botulinum toxin type A. a single dose of 1500 U (units) is injected into the affected upper limb. the placebo consists of 3 ml of sterile saline (NaCl) injected in the same manner.

    To reduce discomfort during the injection, you may inhale a gas mixture called Entonox, which contains nitrous oxide and oxygen. the prescribed amount for the procedure is a total of 36 L of the gas mixture.

  3. Step 3

    Short‑term monitoring after injection

    After the injection you remain in the clinic for a brief observation period. staff check for any immediate reactions such as pain, weakness, or other side effects and record them.

  4. Step 4

    First follow‑up visit (6 weeks)

    Six weeks after the injection you return for the first follow‑up assessment. you complete the Patient Global Impression‑Change (PGI‑C) questionnaire, which asks you to rate how your tremor has changed since the injection.

    The clinician also evaluates your tremor using several scales, measures the strength of the injected hand with a manual dynamometer, and asks you to fill out the quality‑of‑life questionnaire (PDQ‑39) and the daily‑activities questionnaire (MDS‑UPDRS part 2). any adverse events that occurred during the six‑week period are recorded.

  5. Step 5

    Crossover injection (second period)

    After the first follow‑up you receive the opposite treatment. if you previously received the active botulinum toxin, you now receive the saline placebo; if you received placebo first, you now receive the 1500 U Dysport injection. the same injection procedure and optional Entonox inhalation are used as described in step 2.

  6. Step 6

    Second short‑term monitoring after crossover injection

    You stay briefly in the clinic after the second injection for monitoring, as in step 3.

  7. Step 7

    Second follow‑up visit (6 weeks after crossover)

    Six weeks after the second injection you attend the final study visit. you again complete the PGI‑C questionnaire and the same set of clinician‑assessed scales and strength measurements. all side effects and any new adverse events are documented.

  8. Step 8

    Study completion

    After the second follow‑up visit the trial ends for you. the collected data are used to compare the effects of the botulinum toxin and the placebo on your resting tremor.

Who can join the trial?

7 criteria

  • Be diagnosed with Parkinson's disease using the standard UKPDSBB guidelines that doctors use to confirm the condition.
  • Be a man or woman aged between 40 and 80 years.
  • Have a resting tremor (shaking that occurs when the arm is relaxed) that is considered troublesome, scoring at least 3 on the Clinical Global Impression‑Severity (CGI‑S) scale, and that continues even after trying at least two medicines such as levodopa (a drug that replaces dopamine), a dopaminergic agonist (a medication that mimics dopamine), or an anticholinergic (a drug that reduces certain brain signals).
  • Never have received a botulinum toxin injection before (be “naïve” to this treatment).
  • Be taking Parkinson’s medicines that have not changed for at least four weeks before joining the study and must stay the same during the study.
  • Have health coverage through a social security or similar insurance program.
  • Sign a free, informed, written consent form, agreeing to take part, before any study procedures are done.

Who cannot join the trial?

12 criteria

  • Having tremors that are caused by a condition other than Parkinson’s disease.
  • Being under legal guardianship, tutorship, or curatorship (meaning a court has appointed someone to make decisions for you).
  • Having muscle atrophy (muscle wasting or shrinkage) in the muscle that would be treated.
  • Having a urinary tract infection (bladder infection) at the time of treatment if you also experience urinary incontinence (loss of bladder control) due to nerve problems that cause the bladder muscle to overact.
  • Having a past history of problems with swallowing or breathing (respiratory disorders).
  • Having significant problems with nerve‑to‑muscle communication (neuromuscular transmission deficits), such as myasthenia gravis (a disease that makes muscles easily tired).
  • Having a fixed contracture (a permanent tightness of a muscle or joint that cannot be moved).
  • Having an atypical parkinsonian syndrome (a disorder that looks like Parkinson’s disease but is a different condition).
  • Taking medicines that can cause or worsen tremors, such as lithium, sodium valproate, levetiracetam, benzodiazepines, corticosteroids, thyroid hormones, ciclosporin, alcohol, tricyclic antidepressants, theophylline, terbutaline, or antipsychotics (except clozapine).
  • Being allergic (hypersensitive) to the study drug itself or to any of its ingredients, such as human albumin or lactulose.
  • Being pregnant or breastfeeding.
  • Being a woman of child‑bearing age who is not using an effective method of birth control.
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.

We usually reply within a few days

Verified sites

All sites with verified contact details – recruitment status may not be available; ask directly

Trial locations

Where you can join this trial

Countries are shaded by recruitment status. Click a recruiting country to ask about joining there.

Not yet recruiting
Not finding your country?

Not sure what to do next?

Joining a clinical trial can seem overwhelming. We guide you step by step, so you know exactly what to expect and how we support you through the process.

See the full process and FAQ

Investigated drugs

  • Dysport

    is an injectable medication that contains a purified form of botulinum toxin type A. In this study it is given as an injection into the muscles of the upper arm that have a troublesome resting tremor. The toxin works by temporarily blocking the signals that tell the muscle to contract, which can reduce the intensity of the tremor. The trial compares how patients feel after receiving Dysport with how they feel after a placebo injection, to see if the toxin can provide meaningful relief for tremor that does not respond to other treatments.

  • Entonox

    is a gas mixture of nitrous oxide and oxygen that is inhaled through a mask. It is used in the study to help keep patients comfortable during the injection procedure. By providing mild pain relief and a feeling of relaxation, Entonox helps ensure that the injection can be given without causing significant discomfort, but it is not being tested as a treatment for tremor itself.

What is already known about the treatment

  • Dysport 500 U, poudre pour solution injectable

    It is supplied as a sterile powder that is mixed with liquid to form a clear solution and given by injection directly into the affected muscle. Botulinum toxin type A is an approved and widely studied drug used for muscle spasticity, cervical dystonia, and cosmetic reduction of wrinkles, and it is now being tested for Parkinson‑related hand tremor. The toxin works by blocking the release of the chemical messenger acetylcholine at the nerve‑muscle junction, which stops the muscle from contracting. Pharmacologically it is classified as a neurotoxin and a neuromuscular blocking agent.

  • Entonox 50%/50% gaz medicinal comprimat

    Entonox is a compressed gas containing equal parts nitrous oxide and oxygen that is inhaled through a mask or mouthpiece. It is an established analgesic commonly used for pain relief during labor, minor procedures, and emergency care, and it is well documented in medical literature as a safe short‑term inhalation analgesic. The nitrous oxide component depresses nerve activity in the brain, producing a feeling of relaxation and reduced pain, while the oxygen ensures the patient continues to receive adequate breathing support. It is classified as an inhaled analgesic and a nitrous‑oxide‑based anesthetic gas.

Investigated diseases

Parkinson disease - Parkinson disease is a brain disorder that affects movement. It develops gradually, often starting with a slight tremor or stiffness in one hand. Over time, symptoms can spread to other limbs, causing slower movements and balance problems. The condition may also reduce facial expression and change speech. Symptoms usually become more noticeable as the disease advances.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2026-525862-23-00Protocol codeRC31/25/0444Estimated enrolment39 patientsSponsorCentre Hospitalier Universitaire De Toulouse

sourced from the EU Clinical Trials Register and site verification

Want to learn more about this trial or check if you can participate?

Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.

ClinicalTrials.eu

Every clinical trial in Europe, in plain language.

Explore the full ecosystem of clinical research in Europe.

Search trials

Legal notice · Published by CTIN POLAND sp. z o.o., ul. rtm. Witolda Pileckiego 67/109, 02-781 Warsaw, Poland · KRS 0001111334 · REGON 528919042 · NIP 9512598637

© 2026 Clinical Trials EU – European Clinical Trials Information Network

GDPR compliance, ISO 9001 and ISO 27001 certified (LL-C Certification)

On this site, “treatment” means an investigational medicine being studied in a clinical trial. Its safety and efficacy for the use being studied have not yet been confirmed, some participants may receive a placebo or a comparator medicine, and taking part does not guarantee any health benefit. The decision to take part is made by the doctor at the research site. This site is for information only and does not replace medical advice.

This service is not affiliated with the European Commission, the EMA, or the official CTIS system. Most information comes from publicly available international clinical-trial registries, supplemented by data from academic sites, national regulators and commercial sponsors. On this site, “treatment” and “therapy” mean a medicine being tested in a clinical trial. Its safety and effectiveness in the use being studied are not yet confirmed, some participants may receive a placebo or a comparator, and taking part does not guarantee a health benefit. The doctor at the research site decides who can take part. This site provides information, not medical advice. Certain content and visual elements on this website have been generated or enhanced using artificial intelligence (AI).