Fixed-dose combination therapy for Parkinson's disease with a spotlight on entacapone in the past 20 years: a reduced pill burden and a simplified dosing regime.

Parkinson's disease (PD) is a progressive, chronic neurodegenerative disorder. The main neuropathological cause of the disease is the death of dopaminergic neurons in the substantia nigra. Unfortunately, there is no curative treatment yet. The gold-standard of the treatment is levodopa (LD). During the course of the disease, motor complications develop, which postulates the addition of entacapone (ENT) to the dopaminergic medication. Previous studies have suggested that patients have a better quality of life when entacapone is added in a combination with LD. A systematic literature search was performed. Articles were identified through PubMed (MEDLINE), Web of Science, Ovid, and ClinicalTrials.gov databases. The following search terms were used: 'Levodopa' AND 'Carbidopa' OR 'Benserazide' AND 'Entacapone'. The search period was between 2000 and 2020. Twenty randomized and 10 non-randomized clinical trials (12,893 subjects) were included in the qualitative analysis. The systematic review was written in line with the PRISMA guideline. ENT administered in combination with LD resulted in a better quality of life compared to separate tablets. Therefore, in PD patients where impaired motor performance develops and the application of entacapone is necessary, it is suggested to be administered in a single tablet form.