Formulation of bi-layer matrix tablets of tramadol hydrochloride: Comparison of rate retarding ability of the incorporated hydrophilic polymers

Bi-layer tablets of tramadol hydrochloride were prepared by direct compression technique. Each tablet contains an instant release layer with a sustained release layer. The instant release layer was found to release the initial dose immediately within minutes. The instant release layer was combined with sustained release matrix made of varying quantity of Methocel K4M, Methocel K15MCR and Carbomer 974P. Bi-layer tablets were evaluated for various physical tests including weight variation, thickness and diameter, hardness and percent friability. Drug release from bi-layer tablet was studied in acidic medium and buffer medium for two and six hours respectively. Sustained release of tramadol hydrochloride was observed with a controlled fashion that was characteristic to the type and extent of polymer used. % Drug release from eight-hour dissolution study was fitted with several kinetic models. Mean dissolution time [MDT] and fractional dissolution values [T25%, T50% and T80%] were also calculated as well, to compare the retarding ability of the polymers. Methocel K15MCR was found to be the most effective in rate retardation of freely water-soluble tramadol hydrochloride compared to Methocel K4M and Capbomer 974P, when incorporated at equal ratio in the formulation.

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

Evaluation of ethylcellulose as matrices for controlled release drug delivery

As the efficiency of a matrix forming polymer in sustaining drug release is a multiple function of physico-chemical nature of the active ingredient and pH of the surrounding environment, the study was undertaken to evaluate the effect of pH of dissolution media on the release profile of three drug molecules with diversified physico-chemical properties. Matrix tablets of diclofenac sodium, theophylline and diltiazem HCl were prepared using ethylcellulose as the matrix forming agent. The drug dissolution behavior of the matrix tablets were studied over 10 hours in buffer media of pH 1.2, 4.5 and 6.8. Elevation of pH of the dissolution medium increased the rate and extent of diclofenac release. However, for diltiazem HCI, increasing the pH showed the reverse pattern. Theophylline release, on the other hand, seemed to be unaffected by the pH of the dissolution media. This can be correlated with the physicochemical characteristics of the drugs. Effect of compression force on drug release and tablet hardness was also studied. Increasing the compression force reduced drug release irrespective of the chemical nature of the drug molecule which can be attributed to the reduction of porosity and formation of continuous polymeric network within the matrix. Again, no significant change in tablet hardness was found with the increment of compression force. A near zero-order release kinetics were observed in all formulations investigated