Botulinum Toxin Type A for Pain in Advanced Parkinson's Disease.

Background and Objective Pain is a frequent symptom in Parkinson's disease (PD), and the therapeutic alternatives are scarce. The goal of this trial was to measure the effects of botulinum toxin type A (BTXA) in the treatment of limb pain in advanced PD. Methods A randomized double-blind crossover versus placebo study of BTXA for limb pain in advanced Parkinson's disease was conducted. Subjects received individualized BTXA/placebo dosing per pain distribution in limbs. The primary outcome was a measure of change in global pain on a numeric rating scale (NRS) at 4 and 12 weeks postinjection and on a visual analogue scale 12 weeks after treatment. Secondary outcomes included the percentage of responders, physician-rated clinical global impressions, MDS-UPDRS and PDQ-39 scores, and adverse events. Results A total of 12 subjects completed the trial. Treatment with BTXA (average dose=241.66 U) produced a significant reduction in NRS score 4 weeks after the injections (-1.75 points, range from -3 to 7, p=0.033). However, there was no significant difference compared to placebo (p=0.70). Participants with dystonic pain showed a greater reduction in NRS score after 4 weeks when treated with BTXA (2.66 points vs. 0.75 for placebo). There were no significant differences for any of the secondary outcomes or significant adverse events. Conclusions Targeted BTXA injections were safe in patients with limb pain and advanced PD; however, the present study failed to show a significant effect when compared to placebo. Further studies may be focused on evaluating the effect of BTXA particularly in dystonic pain.