Novel gastroretentive dosage forms: Evaluation of gastroretentivity and its effect on levodopa absorption in humans

Purpose. To design novel expandable gastroretentive dosage forms (GRDFs) and evaluate their gastroretentive properties. Then, to assess the pharmacokinetics of levodopa compounded in such a GRDF in healthy volunteers. Methods. Thin (<0.07 cm), large-dimensioned (≥ 5 × 2.1 cm), multi-layer dosage forms (DFs) with different rigid polymeric matrices and mechanical properties were folded into gelatin capsules and were administered to healthy volunteers with a light breakfast. GRDF unfolding and physical integrity were evaluated in vitro and in vivo (by gastroscopy and radiology). The pharmacokinetics of levodopa-GRDF were compared to Sinemet CR® in a crossover design. Results. The combination of rigidity and large dimension of the GRDFs was a decisive parameter to ensure prolonged gastroretentivity (≥ 5 h). Large-dimension DFs lacking rigidity had similar gastroretentivity as a nondisintegrating tablet (10 mm). The GRDFs rapidly unfolded and maintained their mechanical integrity. The absorption phase of levodopa was significantly prolonged following GRDF administration in comparison to Sinemet CR®. Conclusions. The combination of size and rigidity of the novel GRDF enables a significant extension of the absorption phase of a narrow absorption window drug such as levodopa. This approach is an important step toward the implementation of such GRDFs in the clinical setting.