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.