POROUS PLASTIC MATRIX TABLETS OF LEVETIRACETAM FOR ZERO-ORDER CONTROLLED RELEASE: DEVELOPMENT AND FORMULATION OPTIMIZATION

Objective: The prior objective of the current research work was to develop once-daily levetiracetam extended/controlled-release tablets having zero-order release kinetics with the plastic matrix as the release retarding element. For a high water-soluble drug, the formulation of a dosage form so as to have an extended drug release has always been a difficult task. Methods: In the current work, levetiracetam which is a highly soluble drug was taken as the model drug for which extended-release matrix tablets were developed using varied plastic polymers like Polyvinyl acetate (PVAc), Polyvinyl chloride (PVC), Eudragit RSPO and Eudragit RLPO. PVP was considered as a pore-forming agent and PEG 6000 was taken as a water regulating agent. The porous plastic matrix tablets were prepared by embedding the drug in solvent-activated polymer dispersion followed by drying, sieving, mixing with other excipients and finally compressed. Including physical characterization studies and drug release studies, the tablets were subjected to SEM studies before and after the dissolution studies to analyze the effect of the pore former. Results: Pre-compression mixtures exhibited good packageability of 81-92% and hence the compressed tablets were strong enough with good tensile strength in the range of 0.78–0.90 N/mm2. Drug release study results showed that the drug release was controlled for a period of 12–24h. PVAc had shown better controlled-release among all the plastic polymers taken. PEG 6000 in combination with PVP produced the desired zero-order drug release. Conclusion: The levetiracetam porous plastic matrix tablets were developed with zero-order drug release that was effectively controlled for 24hr.

An experimental method for the investigation of rigid polyurethane foams in shear

Widespread applications of rigid polyurethane and plastic foams lead to shear deformations. Therefore, methods for ensuring shear using experimental investigations are necessary, including the possibility of determining the shear modulus, strength and limit angle. Therefore, a device that allows investigating the shear properties of highly porous plastic foams was developed. The proposed device comprises a clip-on extensometer, commonly exploited in uni-axial compression/tension tests, for the determination of the shear displacement directly on the foams’ sample, on a measurement zone of certain dimensions and location. An innovative construction of the extensometer’s legs is elaborated, permitting to investigate the shear displacement field for different dimensions of the measurement zone. Precision of the device is examined by performing a penetration test on materials of different densities: (a) polyurethane foams and (b) wood. Technology for the production of isotropic polyurethane foams as a test material is described in detail. Experimental determination of shear modulus and strength of one and the same sample, in one and the same experiment is elaborated. Displacements in different zones of sample’s work beam are investigated. Experimental data are compared with the results of mathematical modelling and a good correlation is proved to exist.