Tolcapone improves outcomes in patients with Parkinson disease treated by levodopa/carbidopa intestinal gel: A pilot study

Abstract

Background: Patients with Parkinson disease (PD) treated with levodopa/carbidopa intestinal gel (LCIG) have higher prevalence of hyperhomocysteinemia and peripheral nerves damage. Objective: The aim of our study was to test the effect of catechol-O-methyl transferase inhibitor tolcapone - as an add-on therapy to LCIG in patients with PD - on homocysteine (HCY) metabolism and nerve conduction study (NCS) parameters. Methods: We evaluated NCS and serum B12, folic acid, and homocysteine in 16 patients with advanced PD on LCIG. Quality of life (QoL) was also assessed. Six subjects were treated with tolcapone add-on therapy (and LCIG dose reduction), 5 with B vitamin supplementation, and 5 without additional treatment. Results: The level of HCY increased among patients without treatment (4.95 ± 12.54), and decreased in the vitamin (-17.73 ± 11.82) and tolcapone groups (-8.81 ± 8.36). Patients with tolcapone demonstrated improvement in polyneuropathic symptoms and signs compared with patients treated with vitamins or those without additional treatment (-0.83, d = 0.961). Although the most robust improvement in NCS parameters were observed with tolcapone, the findings were inconsistent to prove the effect of any intervention. Only tolcapone treatment was associated with improvement in QoL (d = 1.089). Conclusion: Our study indicates potential of tolcapone add-on therapy in LCIG treated patients in control of homocysteine levels, and improvement of polyneuropathic symptoms, as well as QoL.