Theophylline loaded gastroretentive floating tablets based on hydrophilic polymers: preparation and in vitro evaluation

This investigation describes the preparation and in vitro evaluation of gastroretentive floating tablet of theophylline. Two hydrophilic cellulose derivatives, Methocel K100M and Methocel K15MCR were evaluated for their gel forming and release controlling properties. Sodium bicarbonate and citric acid were incorporated as gas generating agents. The effects of soluble components [sodium bicarbonate and citric acid], gel forming agents and amount variation of theophylline on drug release profile and floating properties were investigated. Tablets were prepared by direct compression technique. Formulations were evaluated for in vitro buoyancy and drug release study was evaluated for eight hours using USP XXII paddle-type dissolution apparatus using 0.1N HCl as dissolution medium. The release mechanisms were explored and explained with zero order, first order, Higuchi and Korsmeyer equations. The release rate, extent and mechanisms were found to be governed by polymer and floating agent content. The content of active ingredient was also a vital factor in controlling drug release pattern. It was found that polymer content and amount of floating agent significantly affected the mean dissolution time, percentage drug release after 8 hours, release rate constant and diffusion exponent

Effect of channeling agents on the release pattern of theophylline from kollidon SR based matrix tablets

The purpose of the present study was to investigate the effect of channeling agent on the release profile of theophylline from Kollidon SR based matrix systems. Matrix tablets of theophylline using Kollidon SR which is plastic in nature were prepared by direct compression process. NaCl and PEG 1500 were used as channeling agents. Drug release study was evaluated for eight hours using USP 22 paddle-type dissolution apparatus using distilled water as the dissolution medium. The release mechanisms were explored and explained with zero order, Higuchi, first order and Korsmeyer equations. The release rate, extent and mechanisms were found to be governed by the type and content of the channeling agents. Increased rate and extent of the drug release were found by using higher content of channeling agent [42.49%] in the matrix due to increased porosity when compared with the formulation having no channeling agents. On the other hand decreased rate and extent of drug release were observed in the formulation having lower channeling agent content [19.76%]. PEG 1500 ensures maximum release of drug from Kollidon SR than NaCl when other parameters were kept unchanged. It was found that type and amount of channeling agent significantly affect the time required for 50% of drug release [T50%], percentage drug release at 8 hours, release rate constant [K] and diffusion exponent [n]. Kinetic modeling of dissolution profiles revealed drug release mechanism ranges from diffusion controlled or Fickian transport to anomalous type or non-Fickian transport, which was mainly dependent on the type and amount of channeling agents. These studies indicate that the proper balance between a matrix forming agent and a channeling agent can produce a drug dissolution profile similar to a desired dissolution profile