Formulation and Evaluation of Gastro-retentive Floating Multi-particulate System of Metoprolol Tartarate

Purpose: To develop a floating multiparticulate unit system for metoprolol tartarate, using a porous carrier, with an outcome for delayed gastric emptying. Methods: Dried microparticles of metoprolol tartarate were prepared by solvent evaporation using Eudragit ® RS-PO, polypropylene foam powder, and dichloromethane as release-rate modifying polymer, floating aid and solvent respectively. The surface topography of the particles was assessed by SEM while the physical state of the drug within the developed system was characterised by DSC and XRD. Drug release was investigated by in vitro dissolution test. Tc99m sulfur colloid radio-labelled microparticle formulation was administered to fasting rabbits and their transit behavior was monitored using gamma scintigraphy. The anterior and posterior images recorded were computed to determine the geometric mean counts, enabling quantitative estimation of gastric emptying rate. Results: Dried free-flowing, white coloured microparticles were obtained. They were highly porous and also irregular in shape. The drug in the microparticles was partly amorphous, showing a decrease in crystallinity. In vitro drug release from the particles followed a biphasic pattern with zero-order kinetics. The microparticulate system exhibited good floating ability with t1/2 of 300 min over the duration of the in vivo study (6 h). Conclusion: The developed microparticles showed suitable release properties, were free-flowing and exhibited good floating ability in rabbit stomach. Therefore, the formulation is capable of being further processed into tablet and/or capsule dosage forms for oral administration as a gastro-retentive controlled delivery system.