Development of Gabapentin Expandable Gastroretentive Controlled Drug Delivery System.

Expandable drug delivery systems are one of many gastroretentive delivery systems which have emerged during the last few years. Expandable systems are usually folded in a capsule and expand to dimensions greater than the pyloric sphincter upon contact with gastric fluid. This prevents them from being evacuated by gastric emptying. The main objective of developing such systems is to increase the residence time of a specific drug in stomach; controlling its release, increasing its bioavailability and decreasing its side effects and dosing frequency. An expandable gastroretentive drug delivery system containing Gabapentin was developed using experimental design (D-optimal reduced quadratic design). This system was able to unfold at stomach pH in less than 15 minutes and obtain a controlled release of 78.1 ± 4.7% in 6 hours following zero-order release kinetic model. It is rigid in stomach and its rigidity decreases at intestinal pH. FTIR analysis indicated the occurrence of hydrogen bonding in Gabapentin when present in the developed system, which might be responsible for the drug's controlled release. XRD analysis indicated that Gabapentin physical properties changed from crystalline in the typical state to amorphous in the developed system.

Tailoring the release rates of fluconazole using solid dispersions in polymer blends.

Formulations of the drug Fluconazole with different release characteristics were prepared by dispersing the active pharmaceutical ingredient (API) in various polymeric carriers, and especially in polymer blends. Fluconazole was tested as a model drug with low solubility in water. First solid dispersions in pure polymers were studied. Use of pure polyvinylpyrrolidone (PVP) as carrier even for high drug load (30 wt%) resulted in rapid release. The drug release rates decreased by increasing the API content. The dissolution rate enhancement was attributed to drug amorphization, particle size reduction, and possible improvement of the drug wetting characteristics. Hydroxypropyl methylcellulose (HPMC) gave solid dispersions, from which the release rates of the drug varied from immediate to sustaining. As the drug amount increased, the rates became higher. Similar behavior also was found when Chitosan was used as carrier, with much more controlled rates close to those for sustained release. These differences were mainly attributed to the limited solubility and swelling of HPMC and Chitosan in aquatic media. To study the effectiveness of polymer blends in adjusting the release rates of the drug, solid dispersions in PVP/HPMC and PVP/Chitosan miscible blends were studied. The release rates of Fluconazole were adequately adjusted by differentiating the weight ratio of the polymers in the blends. PVP/HPMC blends with high PVP content can be used for immediate release formulations but PVP/Chitosan blends are inappropriate for such formulations and can only be used for controlled release.