Abstract #13: Low-Dose Naltrexone's Tolerability and Effects in Fatigued Patients with Parkinson's Disease: An Open-Label Study

Abstract

Introduction One third of idiopathic Parkinson's disease (IPD) patients report fatigue as their most disabling symptom, and 58% consider fatigue to be one of their three most disabling symptoms. The use of low-dose naltrexone (LDN), 4.5 mg qhs, has been anecdotally reported to improve fatigue in IPD. Methods We are examining the tolerability and effectiveness of LDN in patients with parkinsonism in an ongoing open-label trial. Fatigue and motor symptoms in the “On” state are being assessed at baseline and every 4 months over 1 year using the Parkinson Fatigue Scale (PFS-16) and the Unified Parkinson's Disease Rating Scale (UPDRS), respectively. Global Satisfaction of Treatment is also being assessed. We report here on the changes in fatigue and motor scores among the 4 IPD subjects who were fatigued at baseline, defined as a score of e 53 on the PFS-16. We also compare the fatigue changes with those from previous trials in fatigued IPD and multiple sclerosis (MS) patients. Results Eight subjects have been enrolled since January 2009. The 4 IPD subjects who were fatigued at baseline have experienced a mean 22% reduction in PFS-16 scores (range 13–30%) and a 15% increase in total UPDRS “On” scores after 8 months of LDN therapy. Mean Global Satisfaction of Treatment at 8 months was 8.75 on the 10-point scale. No side effects have been associated with LDN therapy among the 8 subjects. Based on previous randomized controlled trials (RCTs), the only effective therapy for fatigue in IPD has been methylphenidate, which showed a 16% decrease in fatigue from baseline. The three therapies demonstrating effectiveness in treating fatigue in MS patients in RCTs have been amantadine, modafinil, and aspirin, which decreased fatigue by 24%, 20%, and 18% from baseline, respectively. Modafinil was shown to be ineffective in treating fatigue in IPD. Conclusions In this small, open-label trial, LDN therapy was well tolerated and was associated with equivalent reductions in fatigue compared with historical benchmarks. These observed reductions in fatigue are unlikely to have been a function of any perceived improvements to motor symptoms, because UPDRS scores slightly worsened over the 8-month trial, as expected in this progressive disease.