Double-layer Tablets of Lornoxicam: Validation of Quantification Method, In vitro Dissolution and Kinetic Modelling

Purpose: To formulate double-layer tablets of lornoxicam (LRX) prepared by direct compression method and evaluate their physical and drug release characteristics.
Methods: The outer layer of tablets, composed of microcrystalline cellulose (MCC), starch and lactose, incorporated tan initial or prompt dose of the drug (4 mg) for immediate release. Hydroxypropyl methylcellulose (HPMC), polyvinylpyrrolidone (PVP K90) and carbomer, in varying concentrations, were used to prepare the tablet cores for sustained drug delivery. Weight variation, dimensions, hardness, tensile strength, friability and disintegration time of the tablets were evaluated. Drug release from double-layer tablets as well as kinetic models of drug release were determined after validating the method used for the quantification of the drug. The analytical method for quantification of LRX by UV spectroscopy was validated and verified for linearity, intra-day and inter-day precision, accuracy, recovery and specifity.
Results: Tablet cores based on HPMC and HPMC:PVP K90 mixture displayed better compression and flow properties (good and fair to passable) than those formulated with PVP K90 and carbomer (poor). Satisfactory results were obtained from all the tablet formulations met compendial requirements. The slowest drug release rate was obtained with tablet cores based on PVP K90 (1.21 mg%.h^-1). Drug release followed Higuchi kinetic model and the tablet cores released drug by diffusion/polymer relaxation or diffusion/erosion.
Conclusion: Double-layer tablet formulation of lornoxicam based on HPMC or HPMC-PVP mixture is suitable for the treatment of inflammatory and painful conditions.

Keywords
Lornoxicam; Controlled release; Double-layer tablets; Non-steroidal antiinflammatory drug; Oral delivery