Design and In-Vitro Evaluation of Floating Tablets of Gabapentin

Gastro retentive system can remain in the gastric region for several hours and hence prolongs the gastric residence time of drugs. The present research work was an attempt to formulate and in-vitro evaluate gastro retentive floating drug delivery system containing Gabapentin in the form of tablets using polymer like HPMC K100M and sodium bicarbonate, citric acid as gas generating agent. A 32 factorial design was applied systematically; the amount of HPMC K100M (X1) and amount of citric acid (X2) were selected as independent variables. The floating lag time, percentage drug release at 6 hr (Q6) and percentage drug release at 12 hr (Q12) were selected as dependent variables.  The tablets were prepared by direct compression method. The tablets were evaluated for the pre and post compression parameters such as weight variation, thickness, friability, hardness, drug content, in-vitro buoyancy studies, and in-vitro dissolution studies and results were within the limits. Hardness was found to be in the range 5.1±0.13 kg/cm2 to 7.1±0.36 kg/cm2, the percentage friability was in the range of 0.30% to 0.82% w/w, and tablets showed 99 to 101.10 %w/w of the labeled amount of Gabapentin indicating uniformity content. The in-vitro dissolution studies were carried out in a USP type-II apparatus in 0.1N HCl. Among all the formulations (GFT1 to GFT9) prepared, batch GFT7 was the best formulation which showed buoyancy lag time 5 sec  and the tablet remained buoyant for >12h. At all the strengths of the polymer tested HPMC K100M and citric acid gave relatively optimum release of gabapentin over 12 h when compared to other formulations. The tablets containing Gabapentin released 92.09 to 99.06% of drug release at the end of 12 hr by in-vitro drug release study. The in-vitro data is fitted in to different kinetic models and the best-fit was achieved with the Higuchi model. The optimized formulation GFT7 followed zero order release kinetics followed by non-Fickian diffusion.