Effect of meal timing on the kinetic-dynamic profile of levodopa/carbidopa controlled is release in parkinsonian patients

Abstract

Objective: The aim of the study was to assess the effect of the time of ingestion of a meal on the pharmacokinetics and pharmacodynamics of a levodopa/carbidopa controlled-release formulation in parkinsonian patients on chronic levodopa therapy.

Methods: The kinetic-dynamic profile of one tablet of controlled-release levodopa/carbidopa 200/50 mg was monitored in eight patients, according to an intrasubject randomized cross-over design in two different sessions. A standard meal was consumed by the patients after they had fasted for 15–17 h, on one occasion 30 min before the ingestion of the test dose, and on the other occasion 2 h after the ingestion of the same drug dose. Blood venous samples for analysis of plasma levodopa and its metabolite 3-O-methyldopa were drawn at 20-min intervals up to 6 h after dosing. Motor response to the levodopa test dose was assessed by the finger tapping and walking speed tests at the same times as blood was drawn.

Results: Controlled is release levodopa intake after meals resulted in a significant delay in drug absorption, with an almost twofold increase in time of initial appearance of levodopa in plasma and time to peak plasma concentration. Peak plasma drug concentrations were not significantly different in the two experimental conditions; the area under the 6-h plasma concentration-time curve showed an average reduction of 24% in the fed condition, partly reflecting the incomplete assessment of levodopa absorption, within the 6 h of examination, due␣to 5-h delayed peak plasma levodopa concentration␣in two patients. With reference to levodopa pharmacodynamics, time to onset of motor response was significantly delayed and duration of motor response significantly curtailed in the fed condition, while the magnitude and overall extent of motor effect were unchanged.

Conclusions: In keeping with previous findings on levodopa standard-release preparations, these data show that time of meal ingestion is an important determinant of levodopa disposition, even from controlled-release preparations in parkinsonian patients. From a clinical point of view, these results help to explain some of the delayed, curtailed and even lacking responses that often complicate afternoon motor performances in patients at the more advanced stages of the disease.