Efficacy and safety of clonidine for the treatment of impulse control disorder in Parkinson's disease: a multicenter, parallel, randomised, double-blind, Phase 2b Clinical trial

BACKGROUND

Impulse control disorders (ICDs) are frequently encountered in Parkinson's disease (PD).

OBJECTIVES

We aimed to assess whether clonidine, an α2-adrenergic receptor agonist, would improve ICDs.

METHODS

We conducted a multicentre trial in five movement disorder departments. Patients with PD and ICDs (n = 41) were enrolled in an 8-week, randomised (1:1), double-blind, placebo-controlled study of clonidine (75 μg twice a day). Randomisation and allocation to the trial group were carried out by a central computer system. The primary outcome was the change at 8 weeks in symptom severity using the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease-Rating Scale (QUIP-RS) score. A reduction of the most elevated subscore of the QUIP-RS of more than 3 points without any increase in the other QUIP-RS dimension defined success.

RESULTS

Between 15 May 2019 and 10 September 2021, 19 patients in the clonidine group and 20 patients in the placebo group were enrolled. The proportion difference of success in reducing QUIP-RS at 8 weeks, was 7% (one-sided upper 90% CI 27%) with 42.1% of success in the clonidine group and 35.0% in the placebo group. Compared to patients in the placebo group, patients in the clonidine group experienced a greater reduction in the total QUIP-RS score at 8 weeks (11.0 points vs. 3.6).

DISCUSSION

Clonidine was well tolerated but our study was not enough powerful to demonstrate significant superiority compared to placebo in reducing ICDs despite a greater reduction of total QUIP score at 8 weeks. A phase 3 study should be conducted.

TRIAL REGISTRATION

The study was registered (NCT03552068) on clinicaltrials.gov on June 11, 2018.

Age and time course of long-term motor and nonmotor complications in Parkinson disease

Objective

To determine the time course of hazard for motor and nonmotor milestones of Parkinson disease (PD) in the long term and to investigate whether risk scales nonlinearly with time is instrumental in identifying changes in pathological processes and evaluating disease-modifying therapies in PD.

Methods

Outpatients with PD at the Lyon University Movement Disorders Center were evaluated for 7 clinical milestones in this retrospective cohort study, encompassing 4 domains of PD progression: (1) motor (motor fluctuations, dyskinesias); (2) axial (postural instability and falls, freezing of gait); (3) neuropsychiatric (impulse control disorders, hallucinations); and (4) cognitive (dementia) complications. For each complication, we estimated the outcome-specific hazard using parsimonious smooth parametric Poisson regression models allowing for nonlinear scaling over disease duration, age at diagnosis, current age, and their interaction.

Results

A total of 1,232 patients with PD experienced 1,527 disease-related complications in up to 12 years of follow-up. Specific to each complication, hazard rates increased dramatically starting from diagnosis and were highest for motor fluctuations and lowest for dementia up to 6 years after diagnosis in patients aged 65 years at diagnosis. Nonlinear patterns indicated dramatic changes in the course of PD after 5 years and predicted more severe axial prognosis after 70 years and for motor fluctuations, dyskinesias, and impulse control disorders before 60 years at diagnosis.

Conclusion

Time course of motor and nonmotor milestones in PD is determined by disease duration and age at diagnosis in nonlinear patterns and their interaction. This indicates disease- and age-specific thresholds across the multiple neurodegenerative processes accumulating in PD at different paces.