Eytan Klausner

Expandable gastroretentive dosage forms.

Expandable gastroretentive dosage forms (GRDFs) have been designed for the past 3 decades. They were originally created for possible veterinary use, but later the design was modified for enhanced drug therapy in humans. These GRDFs are easily swallowed and reach a significantly larger size in the stomach due to swelling or unfolding processes that prolong their gastric retention time (GRT). After drug release, their dimensions are minimized with subsequent evacuation from the stomach. Gastroretentivity is enhanced by the combination of substantial dimensions with high rigidity of the dosage form to withstand the peristalsis and mechanical contractility of the stomach. Positive results were obtained in preclinical and clinical studies evaluating GRT of expandable GRDFs. Narrow absorption window drugs compounded in such systems have improved in vivo absorption properties. These findings are an important step towards the implementation of expandable GRDFs in the clinical setting. The current review deals with expandable GRDFs reported in articles and patents, and describes the physiological basis of their design. Using the dog as a preclinical screening model prior to human studies, relevant imaging techniques and pharmacokinetic-pharmacodynamic aspects of such delivery systems are also discussed.

Novel levodopa gastroretentive dosage form: in-vivo evaluation in dogs.

Due to its narrow absorption window, levodopa has to be administered continuously to the upper parts of the intestine in order to maintain sustained therapeutic levels. This may be achieved by a controlled release (CR) gastroretentive dosage form (GRDF). The aim of this work was to develop a novel GRDF, based on unfolding polymeric membranes, that combines extended dimensions with high rigidity, and to examine the pharmacokinetics of levodopa compounded in the GRDF. Levodopa CR-GRDFs were administered to beagle dogs pretreated with carbidopa. The CR-GRDF location in the gastrointestinal tract was determined by X-ray, and serial blood samples were collected and assayed for levodopa. Optimization of the pharmacokinetic profile of levodopa from the CR-GRDFs was carried out based on the in-vitro in-vivo correlation following modifications of the release rates (adjusted by various membrane thicknesses) and drug loads. The successful CR-GRDF maintained therapeutic levodopa concentrations (>500 ng ml(-1)) over 9 h. In comparison to non-gastroretentive CR-particles and oral solution, mean absorption time was significantly extended. These outcomes demonstrate that the CR-GRDF may be used to improve levodopa therapy and can be applied to extend the absorption of other narrow absorption window drugs that require continuous input.

Novel Gastroretentive Dosage Forms: Evaluation of Gastroretentivity and Its Effect on Riboflavin Absorption in Dogs

AbstractPurpose. The purpose of this study was to design novel gastroretentive dosage forms (GRDFs) based on unfolding multilayer polymeric films, to investigate the mechanism of their gastroretentivity in dogs, and to assess the effect of compounding a narrow absorption window drug in a GRDF on the drugs absorption properties. Methods. Dosage forms (DFs) with different dimensions and mechanical properties were administered to beagle dogs with acidic buffer (pH=1.5), whose gastric retention time (GRT) was then determined by X-ray pictures. Concurrent administration of radiopaque markers was used to assess the effect of the GRDF and/or acidic buffer on GRT. The absorption of riboflavin from a prototype GRDF was compared with a nongastroretentive controlled-release DF and to an oral solution of the drug. Results. Large DFs (≥2.5 × 2.5 cm) containing rigid frame had prolonged GRT (>4 h). Administration of 400 mL of acidic buffer (or water) prolonged GRT whereas the GRDF did not cause additional prolongation. The extended absorption phase (>48 h) of riboflavin administered in a GRDF led to 4-fold increased bioavailability. Conclusion. The combination of large dimensions with rigidity produce gastroretentivity that can be used to improve absorption properties of a model of narrow absorption window drugs in the gastrointestinal tract.

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

AbstractPurpose. 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), multilayer 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.

Furosemide Pharmacokinetics and Pharmacodynamics following Gastroretentive Dosage Form Administration to Healthy Volunteers

The objective of this study was to evaluate the pharmacokinetic and pharmacodynamic properties of furosemide following gastroretentive dosage form (GRDF) administration. A furosemide (60 mg) GRDF, releasing the drug during 6 hours in vitro, or an immediate‐release tablet was administered to healthy male volunteers (N = 14) in a crossover design. Food and liquid intake were standardized; urine was collected, weighed, and assayed for furosemide and sodium concentrations. Pharmacokinetics of furosemide following the GRDF administration, as compared to the tablet, showed lower Cmax and indicated a prolonged absorption phase leading to longer mean residence time in the stomach. The sustained input of the drug significantly improved diuretic and natriuretic efficiencies during the first 5 hours and thereby increased the total effects measured over 24 hours. The unfolding controlled‐release GRDF of furosemide improved the pharmacodynamic actions due to the sustained absorption in the stomach and jejunum, which delayed the bodys counteractivity to the drug effect.

Measurements of size distribution and density of a pharmaceutical fat emulsion, using field-programmed sedimentation field-flow fractionation (SdFFF)

AbstractPurpose. The main goal was to establish that sedimentation field-flow fractionation (SdFFF), operated with power based field programming, is effective in the characterization of a commercial emulsion, Medialipide®. This emulsion is used clinically for total parenteral nutrition and it is consisted of a mixture of long-chain triglycerides (LCT, soybean oil) with medium-chain triglycerides (MCT) emulsified by phospholipids. Methods. Different field programming methods were used in the analysis to establish the limits of applicability of the technique. Results. Identical size distribution profiles were obtained under various conditions of the analysis. The density of the droplets was determined by collecting fractions from the SdFFF eluting bands, and analyzing them by photon correlation spectroscopy. The value of density of the oil droplets was changed in the SdFFF data, until best agreement with the PCS values was achieved. The value of density corresponding to the best agreement was considered as the oil density, and it was closed to the weighted average value between soybean and MCT oils. Conclusions. Field programming extends the capabilities of sedimentation field-flow fractionation in handling and characterizing complex and delicate samples as Medialipide®.