Abstract
A new levodopa-carbidopa intestinal gel (LCIG) system featuring a higher levodopa/carbidopa (LD/CD) concentration and viscosity, LCIG-HV, is being developed to reduce the intrajejunal volume of LD/CD that is administered as compared to the current commercial formulation, LCIG-LV. This study characterizes the LCIG-HV formulation and compares it to the LCIG-LV formulation via dissolution testing and a clinical pharmacokinetic bioequivalence study. In vitro release profiles of LD/CD were determined using a USP Dissolution Apparatus 2 with 500 mL of phosphate buffer (pH 4.5) operating at 25 RPM. A single dose, open-label study was conducted according to a two-period, randomized, crossover design in 28 healthy subjects. The point estimate (PE) of the levodopa C(max) geometric mean for the LCIG-HV formulation was 4% higher than that of the LCIG-LV formulation. PEs of levodopa AUC(t) and AUC(inf) geometric means were comparable for both formulations. PEs of carbidopa C(max) , AUC(t) and AUC(inf) geometric means for the LCIG-HV formulation were 3%-5% higher than those of the LCIG-LV formulation. For both formulations, the median T(max) for levodopa was 1.0 and 3.0 hours for carbidopa. The levodopa half-life harmonic mean was 1.6 hour for both formulations. The carbidopa half-life harmonic mean was 1.9 and 2.0 hour, respectively, for the LCIG-HV and LCIG-LV formulations. C(max) , AUC(t) and AUC(inf) of LD/CD carbidopa were comparable for both formulations. The current study demonstrates that the LCIG-LV and LCIG-HV formulations are clinically bioequivalent for LD/CD according to FDA guidance. However, the dissolution method was over discriminatory of formulation differences.