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Delayed early morning turn "ON" in response to a single dose of levodopa in advanced Parkinson’s disease: pharmacokinetics should be considered

¹ Movement Disorders Unit, Service of Neurology and Neurosurgery, DIPRECA Hospital, Universidad de Santiago de Chile, Chile
² Neurosciences Unit, Facultad de Ciencias Médicas, Universidad de Santiago de Chile, Chile

Correspondence to:
Correspondence to:
Dr P Chaná
Universidad de Santiago de Chile, Belisario Prats 1597B, Santiago, Chile; pedrochana@mi.cl

Keywords: motor fluctuations; Parkinson’s disease; pharmacokinetics; delayed early morning turn "ON"; levodopa

The first 150 words of the full text of this article appear below.

The pathophysiology underlying the fluctuations in response following oral levodopa therapy is complex and includes peripheral and central factors. The short half-life of levodopa, erratic gastrointestinal absorption, and competitive transport across the blood–brain barrier have been regarded as factors responsible for the fluctuating plasma and striatal concentrations of levodopa. Indeed, failure of an oral dose to produce an effect or delay in the onset of action have been associated with problems in absorption.^1,2

We studied the pharmacokinetics of levodopa in 19 patients with advanced Parkinson’s disease (12 men, seven women; period of evolution of illness more than 10 years) with and without a delayed response to the first drug dose in the morning (delayed early morning turn "ON"). The patients were selected according to the UK Brain Bank criteria; those who could not tolerate an assessment after 12 hours without taking their antiparkinsonian medication were excluded. All patients signed an . . . [Full text of this article]