۱- Introduction

۲- Materials and methods

۳- Results

۴- Discussion

References

Abstract 

Introduction: Changing drug dosage is common in clinical practice. Recent evidence showed that psychological factors may affect the therapeutic outcome. The aim of this study is to test whether verbal communication about drug dosage changes motor performance and fatigue in Parkinson’s Disease (PD) patients. Methods: We performed clinical (Unified PD Rating Scale), motor (number of finger flexions and perceived fatigue), and electrophysiological measurements (readiness potential, RP) in PD patients during medication-off and medication-on conditions in three groups. The first group got a full dose of L-dopa and was told it was a full dose. The second group got half dose and was told it was half dose. The third group got half dose, but it was told it was a full standard dose. Results: We found that overt half dose was less effective than the full dose for clinical improvement, motor performance, and readiness potential. However, if half dose was given along with verbal instructions that it was a full dose, clinical improvement, motor performance and readiness potential were not significantly different from the full dose. Conclusions: Our findings indicate that verbal communication about dose reduction is as effective as the 50% dose reduction itself, demonstrating that deceptive information about the dose may have an important impact on the therapeutic outcome. Moreover, the supplementary motor area, source of the RP, seems to be involved in this psychological effect.

Introduction

Chronic use of L-dopa for treatment of Parkinson’s Disease (PD) may lead to motor complications which can worsen the quality of life of PD patients and undermine the L-dopa therapy itself [1]. As changing drug dosage is common in clinical practice [2,3], one strategy may imply a Ldopa dose reduction, albeit it could be sometimes limited by patients’ propensity for dopaminergic overtreatment [4]. Recent research uncovered the important role of psychological factors in drug response for PD patients and clarified some of the biological underpinnings. Both placebo and nocebo effects, respectively mediated by patient’s positive and negative expectations, have been found to play a central role in the therapeutic outcome of these patients [5,6]. Furthermore, bradykinesia, rigidity, and resting tremor have shown to be particularly susceptible to placebo effect compared to other domains of PD impairment [7–۹]. Supporting the crucial role of psychological factors in PD treatment are also the open-hidden studies, where the hidden administration of a drug has been found to be less or not at all effective compared to its administration in full view of the patient [10]. Interestingly, it has been recently showed that verbal communication about the cost of a treatment can affect PD patients’ expectations [11]. This study aims to understand the contribution of verbal instructions on the L-dopa response, specifically on motor performance and fatigue perception, in a cohort of PD patients. The L-dopa dose was thus halved, while manipulating patients’ expectations about drug dosage.