Grace Rathnam

Neuropathic pain is intense in nature and difficult to maintain. The main aim of this study is to provide maximum relief from pain.  The objective was to prepare bilayer tablet comprising  of pregabalin and methylcobalamin for effective treatment of neuropathic pain. Methylcobalamin was formulated as immediate release (IR) layer using super-disintegrant sodium starch glycolate (SSG) whereas pregabalin was formulated as sustained release (SR) layer using polymers hydroxypropyl methyl cellulose (HPMCK4M, K100M)  to deliver the drug at sustained manner effective for the treatment of neuropathic pain. The SR layer of pregabalin is prepared by wet granulation method and IR layer of methylcobalamin is prepared by direct compression method. Tablet blends were evaluated through various pre-compression and post-compression tests. Super disintegrant, SSG at 20% concentration produced excellent results for immediate release of methylcobalamin to exert its action and other additional beneficial effects. The K100M and K4M grade of HPMC produced excellent SR efficiency. Optimum formulation released methylcobalamin and pregabalin at 98.92%  in 45 min and 97.81% in 12 h from respective layers. Pre-compression and post-compression parameters of optimized IR layer comprising Methylcobalamin and SR layer comprising pregabalin exhibit satisfactory results. Bilayer tablet of Methylcobalamin and pregabalin prove to be effective as a combination therapy for the treatment of neuropathic pain by sequential release of the drug.

Bioadhesive gels improve both effectiveness and efficiency of the product due to intimate contact between a delivery device and the absorbing cell layer.  The interaction at the functional group level often results in the formation of mixtures capable of exhibiting rheological synergy.  Rheological synergy is the demonstration of greatly excess of viscosity and gel like properties when mixed with mucin than if the mucin and gels were examined separately.  This rheological synergism between gels and mucin could be used as an in vitro parameter to determine the mucoadhesive properties. In this study a simple rheological method is used to quantitatively determine various parameters like viscosity enhancement (ηenhance), relative viscosity enhancement of the combination system (ηrel), force of mucoadhesion (F) and viscosity component of bioadhesion (ηb). This is used to quantitatively compare different bioadhesive nasal gels prepared using carbopol which contain cyclodextrin as absorption enhancer. Composition of a gel can strongly influence its rheological properties and even one different constituent can lead to significantly different rheological behavior. The influence of the presence of cyclodextrin and different methods of addition of cyclodextrin was studied. The pattern noticed in this study was that the gels without the cyclodextrin showed the highest force of bioadhesion which was followed by the gels with cyclodextrin as inclusion complex and then by the gels with cyclodextrin as a physical mixture.  These gels were also subjected to Texture Profile Analysis.