A new slow release formulation of metoprolol: in-vitro and in-vivo evaluation in dogs

Development of a sustained-release microcapsule for delivery of metoprolol succinate

Sustained-release (SR) formulations of metoprolol succinate (MS) may minimize fluctuations in plasma concentration and decrease the resulting adverse events. The aim of the present study was to optimize the loading capacity of microcapsules and the SR of MS. A uniform design method was applied to optimize the formulation of SR microcapsules, composed of ethyl cellulose and polyethylene glycol 6,000, in one step via emulsion-solvent diffusion. In vitro release was studied, and the in vivo bioavailability of MS following dosing with novel microcapsules was compared with a commercially available MS formulation in beagle dogs. The present methodology achieved an entrapment efficiency of 83.2%, with 96.1% of drug released in vitro in 18 h, and the release was close to linear over a 12-h period. Pharmacokinetic studies of MS microcapsules in beagle dogs demonstrated a superior SR profile compared with conventional SR tablets. MS microcapsules were developed with high encapsulation efficiency, which had desirable SR properties in vitro and in vivo.

Development of metoprolol tartrate-loaded sustained-release pellets: effect of talc on the mechanism of drug release

Talc is one of the most commonly used antiadherents in the coating film. However, the mechanism of influence of talc on drug release has yet to be fully understood. In this study, metoprolol tartrate (MT)-loaded Eudragit NE 30 D-coated sustained-release (SR) pellets were prepared using talc as an antiadherent in the layering and coating processes. Talc significantly reduced the stickiness of the layered or coated substrates, thus enhancing the process smoothness. Moreover, the incorporation of talc into the coating film significantly affected drug release. The water vapor permeability and drug permeability of free films increased as the concentration of talc increased. Importantly, talc had a dynamic effect on the drug release. The drug release rate of the pellets in the initial stage (within 2 h) increased with increasing talc concentrations, which exceeded the critical pigment volume concentration resulted in leaks formation in the coated film. However, subsequent swelling of the membrane and expansion of the copolymer network eliminated the influence of talc and the drug release was then controlled by the polymeric membrane. These results suggest that talc contributed to the reduction of the sticking of layered or coated substrates, and facilitated the manufacturing process and drug release properties.