Abstract: Multilayer matrix tablets can be designed for controlled drug delivery wherein one or two layers of release retardant polymer may be applied on the both sides matrix tablet such that the swollen hydrophilic polymer controls the drug release after oral administration. These formulations designed to deliver the drug at predetermined rate, maintain therapeutically effective concentrations in systemic circulation for prolonged period of time. In the present study, guar gum was used as hydrophilic matrix carrier for designing oral controlled drug delivery systems of highly soluble drug tramadol HCl. Three layered matrix tablets of tramadol HCl prepared by wet granulation technique were optimized to release the drug at the desired first order release rate constant of 0.04 hr-1. The release rate was best defined by peppas model and the formulation F8 approaching drug release rate value of 0.04hr-1 was identified as the optimized formulation.
Oral ingestion has long been the most convenient and commonly employed route of drug delivery due to its ease of administration, least aseptic constraints and flexibility in the design of the dosage form. There are many ways to design modified release dosage forms for oral administration and one of them is multi-layered matrix tablet. Multi-layered matrix tablet is a drug delivery device, which comprises a matrix core containing the active solute and one, or more barriers (modulating layers) incorporated during the tabletting process. The modulating layers delay the interaction of active solute with dissolution medium, by limiting the surface available for the solute release and at the same time controlling solvent penetration rate.4 In this device, the coat layers prevent the water penetration, through the protected core for some duration. After this phase, during the subsequent dissolution process, these swollen barriers are erosion dominated and the surface available for drug release slowly increases. In this way the decrease of delivery rate due to the increase of diffusion path-length (saturation effect) is counterbalanced by the simultaneous increase of the area available for drug release.5 Thus by combining a time-dependent control of the hydration rate of the device with the reduction of tablet surface exposed to the dissolution medium, it is feasible to achieve a linear release profile. It is also possible to obtain various dissolution patterns such as multi modal, pulsatile or delayed delivery, extended release (characterized by reasonably constant rate) for different drugs by varying the formulations of layers. In all the applications, the multi-layered system should swell, gel and finally erode completely, leaving negligible residue in the gastro-intestinal tract.