Pain is a relevant and often underestimated non-motor symptom affecting the quality of life of patients with
Parkinson's disease (PD). Although some
pain symptoms can be effectively treated by dopaminergic medication, a correct diagnosis of the different types and distribution of
pain in PD is challenging, and accordingly, its treatment remains troublesome. We evaluated the efficacy and the safety of a prolonged release oral formulation of
oxycodone hydrochloride combined with
naloxone hydrochloride dehydrate, in a fixed ratio of 2:1 (OXN PR). A total of 16 PD patients with history of
pain with a minimum intensity of four on numerical rating scale (NRS) received low-dose OXN PR (5/2.5 mg twice daily) and were observed for a period of 8 weeks. The primary efficacy measure was the
pain severity measured with NRS and Brief
Pain Inventory (BPI). Secondary efficacy measured the safety profile by recording the occurrence of side effects, clinical global impression of change (CGI-C),
Parkinson's disease sleep scale 2 (PDSS-2), Bowel function index (BFI). Data were collected and analyzed using descriptive statistics. Patients who completed the study (14 out of 16) reported a significant
pain relief as observed by the reduction of NRS and BPI scores. No adjustment of dopaminergic
therapy was required. No significant changes were observed in bowel function and
constipation symptoms as measured by the BFI during the 8-week period. Similarly, no changes were observed in PDSS-2 score, whereas an improvement was recorded by CGI-C compared to baseline. Low-dose oral OXN PR was efficacious for the management of
pain symptoms of patients with PD. More importantly, patients did not experience significant side effects, such as
constipation or sedation. Our study provides evidence that
opioids can be used to treat
pain symptoms in PD patients.