Parkinson's Drug Reduces Fibromyalgia Pain - CME Teaching Brief - MedPage Today

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Parkinson's Drug Reduces Fibromyalgia Pain

By Neil Osterweil, Senior Associate Editor, MedPage Today

Reviewed by Jasmer, MD; Assistant Professor of Medicine,

University of California, San Francisco

July 28, 2005

MedPage Today Action Points

* Inform patients that in this small, short duration study, Mirapex

was associated with a greater degree of pain relief than placebo.

* Understand that Mirapex is approved by the FDA only for the

treatment of idiopathic Parkinson's disease.

* Be aware that in this study, subjects were allowed to continue on

their existing medications, which could have altered the results.

* Be aware that the lead author of the study holds patents on the

use of this category of medication in the treatment of fibromyalgia.

Review

RENTON, Wash. July 28-The Parkinson's disease drug Mirapex

(pramipexole) reduced pain and fatigue and improved function in some

patients with fibromyalgia in a small study, reported investigators in

a private rheumatology practice here.

In a randomized trial comparing Mirapex with placebo in 49 patients

with fibromyalgia, patients who received Mirapex experienced gradual

and more significant improvements in measures of pain, fatigue,

function, and global status than patients on placebo, according to

J. Holman, M.D., and Robin R. Myers, M.S., of Pacific

Rheumatology Associates here.

Their findings were published in the August issue of Arthritis &

Rheumatism.

Recent research suggests that pain associated with fibromyalgia may be

caused by abnormal sensory processing in the central nervous system.

Mirapex, a dopamine receptor agonist with particular affinity for the

dopamine3 receptor agonist, could theoretically mitigate symptoms of

fibromyalgia through its effects on dopamine stimulation.

Dr. Holman holds a U.S. patent for the use of dopamine2 and dopamine3

receptor agonists in the treatment of fibromyalgia. Mirapex is

indicated by the FDA only for treatment of idiopathic Parkinson's

disease.

Based on observations of Mirapex's efficacy in treating fibromyalgia in

open-label studies, and for the treatment of restless leg syndrome

(which is more common in patients with fibromyalgia than in healthy

controls) in placebo-controlled trials, the investigators designed the

randomized study.

In this placebo-controlled, parallel group, dose-escalation trial, 60

patients were randomly assigned on a 2:1 basis to either Mirapex or

placebo, respectively. Patients given the active drug were started at a

dose of 0.25 mg at bedtime the first week, with the dose increasing by

0.25 mg/day weekly, to a maximum dose of 4.5 mg/day at weeks 12, 13 and

14. The dose was then tapered to 0 over week 15. Evaluations were

conducted every two weeks, with the final evaluation at week 15.

Exclusion criteria included uncontrolled thyroid disease, substance

abuse, sleep apnea, and cervical myelopathy or severe cervical pain on

extension, among others.

Participants who were on a stable dose of concomitant medications such

as analgesics for at least six weeks prior to study entry were allowed

to continue on those medications during the study, but patients who

started new medications during the study period were dropped. In all,

49 of 60 patients completed the study, which included an

intent-to-treat analysis.

Concomitant medications included narcotics, antiepileptics, NSAIDs,

antidepressants, SSRIs, anxiolytics, muscle relaxants, and hypnotics.

Both placebo-treated and Mirapex-treated patients reported significant

decreases in pain, but the decrease was significantly greater among

patients treated with the active drug. At 14 weeks the decrease in pain

as measured by the pain score on the visual analog scale (VAS) was 36%

among Mirapex-treated patients, and 9% among those on placebo. In the

active drug group, 42% reported a decrease in pain of at least 50%,

compared with 14% of the placebo group.

A post hoc analysis of VAS pain scores showed that 82% of patients

taking Mirapex noted some improvement compared with 57% of those taking

placebo (P =0.04).

Mirapex also appeared to have the edge over placebo in secondary

measures of efficacy, including the Fibromyalgia Impact Questionnaire

score, pain improvement scale, Multidimensional Health Assessment

Questionnaire, VAS fatigue, and VAS global scores.

The most common adverse events in patients taking Mirapex were weight

loss and nausea; patients on placebo also reported nausea, possibly due

to the influence of potentially suggestive language on the consent

form, the authors speculated.

Patients taking Mirapex did not report hallucinations or sleep attacks

that are commonly seen in those taking the drug for Parkinson's

disease.

The authors acknowledged that the study results are limited by the

concomitant use of other medications and by the short duration.

" Finally, it should be noted that some exclusion criteria in this study

were particularly important, " the authors wrote. " Both positional

cervical myelopathy and untreated obstructive sleep apnea are potent

adrenergic arousals that commonly contribute to autonomic

dysregulation. Both conditions limit the efficacy and tolerability of a

D3 agonist when used to treat fibromyalgia. Given the significant

prevalence of cervical pain and obstructive sleep apnea in patients

with fibromyalgia, many may not respond to treatment with pramipexole. "

Primary source: Arthritis & Rheumatism

Source reference:

Arthritis & Rheumatism 2005;52;2495-2505

http://www.medpagetoday.com/Rheumatology/GeneralRheumatology/tb1/1441