ABSTRACT
An orally administered bilayer tablet with Tamsulosin (TAM) as the sustained release (SR) and Finasteride (FIN) as immediate release (IR) was manufactured. A response surface methodology was employed to formulate bilayer tablets with individual release layers, i.e., sustained and immediate release (SR and IR). Independent variables selected in both cases comprise hydroxypropyl methylcellulose (HPMC) as SR polymer, and avicel PH102 in the inner layer while Triacetin and talc in the outer layer, respectively. Tablets were prepared by direct compression, a total of 11 formulations were prepared for inner layer TAM, and 9 formulations for outer layer FIN were designed; these formulations were evaluated for hardness, friability, thickness, %drug content, and %drug release. A central composite design was employed in response surface methodology to design and optimize the formulation. The percentage of drug released was evaluated by in-vitro USP dissolution method of optimized formulation for 0.5, 2, and 6 hrs, and results were 24.63, 52.96, and 97.68 %, respectively. Drug release data was plotted in various kinetic models using a D.D solver, where drug release was first order that is concentration dependent and was best explained by Korsmeyer-Peppa kinetics, as the highest linearity was observed (R2 = 0.9693). However, a very close relationship was also noted with Higuchi kinetics (R2 = 0.9358). The mechanism of drug release was determined through the Korsmeyer model, and exponent "n" was found to be 0.4, indicative of an anomalous diffusion mechanism or diffusion coupled with erosion.
ABSTRACT
The structure of the title compound, 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(piperazin-4-ium-1-yl)-1,8-naphthyridine-3-carboxylate trihydrate, C(15)H(17)FN(4)O(3).3H(2)O, has a zwitterion of enoxacin and three water molecules in the asymmetric unit. The zwitterions form sheets lying parallel to each other and are hydrogen bonded in a head-to-tail manner. The crystal structure is stabilized by the involvement of O and H atoms from all the water molecules in strong hydrogen bonds. The naphthyridine ring system is essentially planar, with the carboxylate group lying out of this plane at an angle of 26.13 (6) degrees and the ethyl group oriented at approximately right angles to this plane. The piperazinium ring adopts a chair conformation.
