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

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What is this study about?

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.

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 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 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 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 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 second short‑term monitoring after crossover injection

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

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 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 Study?

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 Study?

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.

Where you can join this trial?

Verified and Recommended Sites

No sites found in this category

Verified Sites

Site Name	City	Country	Status
Oncopole Claudius Regaud	Toulouse	France

Other Sites

Site Name	City	Country	Status
Cdgszt Hljcalznrzk Uovyueotgqjar Do Nwjeq	Nimes	France

Trial status

Country	Status	Recruitment Start
France	Not yet recruiting	01.09.2026

Trial locations

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.

Investigated Diseases:

Parkinson's disease

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 ID:

2026-525862-23-00

Protocol code:

RC31/25/0444

Trial Phase:

Therapeutic exploratory (Phase II)

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

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?