Circadian phase dependent pharmacokinetics of L-dopa, its main metabolites (3-OMD, HVA, DOPAC) and carbidopa in rats

The effects of a normal protein diet on levodopa plasma kinetics in advanced Parkinson's disease

LevoDOPA given orally may compete with the neutral aminoacids contained in food for its absorption in the small intestine. LevoDOPA plasma kinetics of the morning intake with 'french' breakfast (low protein content) were compared with those of the noon intake with lunch (normal protein content) in 20 advanced parkinsonian patients (mean disease duration: 10 years). The galenic form and the dosage of levoDOPA were strictly the same for morning and noon intakes in each patient. Blood samplings were collected at T0 (just before intake) and successively at 15, 30, 45, 60, 90, 120, 150 and 180 min after intake. LevoDOPA plasma levels were further measured with HPLC method, then giving the following variables: Cmax (peak concentration), Tmax (time corresponding to Cmax), AUC (area under curve). The results showed no significant difference for Cmax and Tmax whereas the AUC was significantly (P < 0.001) increased for the noon intake, due to the trough concentration effect. These data suggest that, since rich protein diet has been shown to impair the clinical effect of LevoDOPA, this protein effect is probably not due to competitive intestinal absorption of LevoDOPA.

Biologic rhythms and Parkinson's disease: a chronopharmacologic approach to considering fluctuations in function

The existence of circadian rhythms and their implication in many pathologic processes have been underlined in several diseases but have not been evaluated in Parkinson's disease. The aim of this paper is to review diurnal variations of clinical, biologic, or experimental factors described with Parkinson's disease. Clinical data often report daily fluctuations of motor activity pattern, but the effect of the stage of the disease and the respective roles of drugs are difficult to evaluate. Sleep disturbances in Parkinson's disease patients also reveal alterations of circadian rhythms. Autonomic dysfunction, described in Parkinson's disease, reveals numerous alterations in circadian regulations including loss of circadian rhythm of blood pressure, increased diurnal blood pressure variability, and postprandial hypotension. Many biologic indices such as cortisol, catecholamines, and melatonin are also altered. Circadian rhythms in dopaminergic systems as well as possible daily fluctuations in kinetics of drug treatments are likely involved in such variations. Few clinical studies have been devoted to circadian patterns of drug response. As for other diseases where biologic rhythms are concerned Parkinson's disease therapy may be influenced by further understanding of circadian influence.

Levodopa-induced drowsiness in healthy volunteers: results of a choice reaction time test combined with a subjective evaluation of sedation

The aim of the present study was to assess levodopa (L-Dopa)-induced drowsiness in healthy volunteers using two parameters: choice reaction time and a subjective rating of sedation. Sixteen subjects participated in a randomized, double-blinded, crossover study. A single dose of 200 mg L-Dopa or placebo was administered at 9:00 AM. To limit peripheral side effects connected with L-Dopa, subjects were treated with 20 mg domperidone three times daily. Subjective rating of sedation consisted of visual analogue scale. Reaction time was measured by means of responses to two light-emitting diodes. The illumination of one of these diodes constituted the imperative signal. Manual responses were performed on two buttons located under the right and left index fingers. Results demonstrated a positive correlation between sedation level and reaction time (r = 0.70, p = 0.0026). Adverse events of L-Dopa were nausea (four cases) and excitation (one case). Subjects who did not develop adverse events were faster under L-Dopa than under placebo (p = 0.02), whereas subjects who had nausea or excitation were slower. A single dose of L-Dopa either deteriorated or improved choice reaction time in healthy volunteers according to whether it was sedative and whether it generated disruptive adverse events.