Concentration-effect relationship of levodopa-benserazide dispersible formulation versus standard form in the treatment of complicated motor response fluctuations in Parkinson's disease

We compared the kinetic-dynamic profile of a postprandial dose of levodopa-benserazide dispersible formulation to that of the standard form in eight patients with parkinsonism presenting delayed or irregular patterns of after-meal levodopa dose effects. Patients were studied on two occasions, one week apart, according to an intrasubject randomized cross-over design. Thirty minutes after the consumption of a standard meal, patients received their usual levodopa-benserazide postprandial dose, on one occasion in the standard formulation and on the other one in the dispersible form. Blood venous samples for analysis of plasma levodopa concentrations were drawn at 15-minute intervals for the first 2 hours, then half-hourly until 5 hours after dosing. Motor response to the levodopa test dose was assessed by the finger tapping test at the same times as blood was sampled. The only statistically significant finding was a shorter time to peak plasma levodopa concentration with the levodopa-benserazide dispersible formulation compared with the standard form, whereas comparisons of levodopa pharmacodynamics skewed little advantage of either formulation. Considering that liquid formulations of levodopa are less practical, we suggest reserving dispersible levodopa-benserazide tablets for selected patients and carefully monitoring drug dose motor response.