• Parkinson Study Group STEADY-PD III Investigators.
• Ann. Intern. Med. 2020 May 5; 172 (9): 591-598.

BackgroundStudies suggest that dihydropyridine calcium-channel blockers may be associated with reduced risk for Parkinson disease (PD).ObjectiveTo assess the effect of isradipine, a dihydropyridine calcium-channel blocker, on the rate of clinical progression of PD.DesignMulticenter, randomized, parallel-group, double-blind, placebo-controlled trial. (ClinicalTrials.gov: NCT02168842).Setting57 Parkinson Study Group sites in North America.ParticipantsPatients with early-stage PD (duration <3 years) who were not taking dopaminergic medications at enrollment.Intervention5 mg of immediate-release isradipine twice daily or placebo for 36 months.MeasurementsThe primary outcome was change in the Unified Parkinson's Disease Rating Scale (UPDRS) parts I to III score measured in the antiparkinson medication "ON" state between baseline and 36 months. Secondary outcomes included time to initiation and use of antiparkinson medications, time to onset of motor complications, change in nonmotor disability, and quality-of-life measures.Results336 patients were randomly assigned (mean age, 62 years [SD, 9]; 68% men; disease duration, 0.9 year [SD, 0.7]; mean UPDRS part I to III score, 23.1 [SD, 8.6]); 95% of patients completed the study. Adjusted least-squares mean changes in total UPDRS score in the antiparkinson medication ON state over 36 months for isradipine and placebo recipients were 2.99 (95% CI, 0.95 to 5.03) points versus 3.26 (CI, 1.25 to 5.26) points, respectively, with a treatment effect of -0.27 (CI, -3.02 to 2.48) point (P = 0.85). Statistical adjustment for antiparkinson medication use did not change the findings. Secondary outcomes showed no effect of isradipine treatment. The most common adverse effects of isradipine were edema and dizziness.LimitationThe isradipine dose may have been insufficient to engage the target calcium channels associated with neuroprotective effects.ConclusionLong-term treatment with immediate-release isradipine did not slow the clinical progression of early-stage PD.Primary Funding SourceNational Institute of Neurological Disorders and Stroke.

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