Propranolol Reduces Tremors in Parkinson Disease Patients
The beta-blocker propranolol reduces Parkinson disease (PD) tremor in both stressful and resting conditions, according to results from a placebo-controlled crossover trial published in the Annals of Neurology.
“The clinical implication of our findings is that propranolol could be a useful additional treatment option for PD tremor, whether or not it is triggered by stress, particularly for tremor responding insufficiently to dopaminergic drugs,” wrote corresponding author Anouk van der Heide, PhD, Center of Expertise for Parkinson and Movement Disorders at Radboud University Medical Centre, Nijmegen, The Netherlands, and study coauthors.
The double-blind study included 27 patients with PD with prominent resting tremor. Although propranolol, which was developed for high blood pressure and heart arrhythmias, is also a standard treatment for essential tremor, researchers were interested in its effect on PD tremor.
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Patients received a single dose of 40-mg propranolol or placebo on 2 separate days. On each, researchers assessed tremor severity with accelerometry and tremor-related brain activity with functional magnetic resonance imaging (fMRI), as well as heart rate and pupil diameter. Measurements were taken both at rest and during a stressful cognitive load task that involved mathematical calculations.
During the task, patients showed increased pupil size and heart rate, reflecting a stress response. As expected, their tremors worsened without medication.
However, during stress as well as at rest, propranolol reduced PD tremors compared with placebo, according to the study. On fMRI, tremor-related activity in the motor cortex decreased after patients took propranolol.
“We know that abnormalities in systems like the dopamine system cause tremors,” said Rick C. Helmich, MD, PhD, study coauthor and neurologist at Radboud University Medical Center. “Based on our study, we now think that the stress hormone noradrenaline acts as an amplifier, which increases tremor intensity in the brain’s movement area. Propranolol inhibits this amplifying effect and thus reduces symptoms.”
Propranolol’s effect on tremors during rest surprised the research team.
“Apparently, our stress system is occasionally active, even at rest,” said Dr van der Heide. “This changes how alert someone is and leads to spontaneous fluctuations in tremors. We previously thought that the stress hormone system was only active under stress, but apparently, that's too simplistic. It also plays a role at rest.”
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