Objective: To determine the efficacy of duloxetine for the management of pain in Parkinsons disease.

Background: Presently there are no clear guidelines for the management of pain in Parkinsons disease. The current practice of dopamine replacement therapy and traditional analgesia has produced mixed results. This study aims to explore the efficacy of duloxetine, a serotonin noradrenaline re-uptake inhibitor for the management of pain in Parkinsons disease.

Method: This was a 6 week prospective double blind placebo controlled trial. Inclusion criteria were Parkinsons disease patients with chronic pain, with Hoehn & Yahr stage I-III on stable doses of regular analgesics. Participants were randomised to either placebo or duloxetine 30mg once daily initially, uptitrated to 60mg once daily after 2 weeks until study completion. Efficacy measures include 11-point Visual Analogue Scale and Short-Form McGill Pain Questionnaire. Additionally, we used an evoked thumbnail pressure pain stimulus  as  a psychophysical measure to determine subjective pain thresholds for just noticeable pain and moderate pain of each participant. A hydraulically driven device consisting of a circular rubber probe attached to a piston was used  to deliver the evoked pain stimuli and  the pain thresholds for each participant were determined using the ‘multiple random staircase method’.1

Results: Twelve participants were recruited and completed the study.  Five participants, 3 females and 2 males were randomised into the duloxetine group. At baseline, there were no statistically significant difference in demographic and clinical data between the duloxetine group and placebo group. There was no statistically significant difference in the Visual Analogue Scale scores between the duloxetine and placebo group at study completion (p=0.64). There were numerical improvements in the Short-Form McGill Pain Questionnaire scores favouring the duloxetine group but this was not statistically significant, p=0.344. In the evoked pain pressure stimulus, there was reduced just noticeable pain thresholds and increased moderate pain thresholds in the duloxetine group as compared to the placebo group, but the results were not statistically significant, with p values of 0.311 and 0.191, respectively.

Conclusion: Further studies are required to determine whether duloxetine has a role in the management of pain in Parkinsons disease.

References: 1. Gracely RH, Lota L, Walter DJ, Dubner R. A multiple random staircase method of psychophysical pain assessment. Pain 1988. 32 (1): 55-63

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MDS Abstracts - https://www.mdsabstracts.org/abstract/duloxetine-for-pain-in-parkinsons-disease-a-single-center-double-blind-randomised-placebo-controlled-trial/