Low pyridoxine levels and its association with the onset of gastrointestinal intolerance to oral levodopa in patients with Parkinson's disease: a cohort study

Abstract

BACKGROUND Parkinson's disease (PD) is the second most common neurodegenerative disease consisting of the presence of motor symptoms, bradykinesia plus stiffness, tremor or instability and other non-motor symptoms. PD has a high prevalence. The etiology of the disease is unknown in most cases although risk factors related to its occurrence have been identified. Its diagnosis is based on the clinic. There is no curative treatment but symptomatic treatments. Several pharmacological groups can be considered in

patients with PD, but still after 50 years of its onset the choice for most patients is L- DOPA, the most effective drug to treat the symptoms of the disease. The progression

of the disease over time implies the need to increase doses of this drug or changes in the form of administration. A high percentage of patients taking this drug have adverse reactions, most of them motor but a considerable percentage also present adverse digestive reactions. In the metabolic pathway of this drug participate some B- complex vitamins such as pyridoxine, cobalamin, folic acid, and other biomolecules such as homocysteine. OBJECTIVE The aim of this study is to assess whether low pyridoxine levels influence the onset of gastrointestinal intolerance to L-DOPA in patients with Parkinson’s disease. DESIGN The study is designed as a multicenter observational prospective cohort study in reference hospitals of Catalonia. PARTICIPANTS All patients with Parkinson's disease who start oral L-DOPA treatment (n=280) and meet the selection criteria will participate in this study. METHODS Pyridoxine and covariate values (B12, folic acid and homocysteine) will be obtained from blood tests. To assess gastrointestinal intolerance patients will respond a survey of gastrointestinal tolerance to L-DOPA within three months of starting treatment. Subsequently we will carry out a statistical analysis to compare which percentage of cases appears in relation to low levels of pyridoxine compared to the group that does not have them low