Pharmacoscintigraphic and pharmacokinetic evaluation on healthy human volunteers of sustained-release floating minitablets containing levodopa and carbidopa

In this study, scintigraphic and pharmacokinetic studies were conducted on 10 healthy, fed volunteers. Two concepts of sustained-release floating minitablets – Levo-Form 1 (matrix) and 2 (coated) – were evaluated and compared to the marketed product Prolopa® HBS 125. All the floating forms were radiolabelled with 111In in order to evaluate their gastric residence time using γ-scintigraphy. It was shown that the three formulations offered almost the same mean gastric residence time, which was about 240 min. Prolopa® HBS 125 and Levo-Form 2 presented intragastric disintegration, which can lead to a more pronounced “peak & valley” effect on the plasma concentration–time profile of levodopa. In contrast, the plasma concentration–time profile of levodopa following the administration of Levo-Form 1 was more evenly distributed. Moreover, Levo-Form 1 provided the lowest variations between men and women in terms of AUC and Cmax values. Finally, when the same amount of inhibitors of extracerebral dopa decarboxylase – carbidopa and benserazide – had been administrated, the mean AUC, Cmax and Tmax values obtained for benserazide were lower than those obtained for carbidopa.