Design and Evaluation of Losartan Potassium Matrix Tablets with Natural and Synthetic Polymers

The objective of the study was to formulate controlled release matrix tablets of losartan Potassium by using a combination of hydrophilic synthetic polymer like poly (ethylene oxides) and natural gums like xanthan gum, karaya gum and guar gum. A combination of synthetic hydrophobic polymers like methacrylates with synthetic hydrophilic polymer like poly (ethylene oxide) was also used in the preparation of matrix tablets and evaluated for their influence on controlled drug release. The matrix tablets were prepared by direct compression process and evaluated for hardness, weight variation, friability, swelling index and for in-vitro release of the drug. Preliminary evaluations showed that matrix tablets containing xanthan gum, guar gum and sodium alginate alone or in combination could not efficiently retard the drug release for prolonged period of time. The tablets containing combination of natural polymers and poly(ethylene oxides) and also methacrylates and poly(ethylene oxides) exhibited controlled release for a prolonged period of time. All the physical characteristics evaluated for the tablets were found to be within the acceptable limits. INTRODUCTION: Oral route has been one of the most popular routes of drug delivery due to its ease of administration, patient compliance, least sterility constraints and flexible design of dosage forms. When the release medium (i.e. water) is thermodynamically compatible with a polymer, the polymer may undergo relaxation process so that the polymer chains become more flexible and the matrix swells. This could allow the encapsulated drug to diffuse rapidly out of the matrix. On the other hand, it would take more time for drug to diffuse out of the matrix since the diffusion path is lengthened by matrix swelling . In the preparation of matrix tablets when a combination of hydrophilic polymers and gums are used, when the tablet is exposed to the dissolution medium the polymers absorb the medium and swells by interacting with each other . This may result in an increase in the viscosity, which becomes greater than the viscosity of each polymer individually. This can be used for extending the drug release for prolonged period of time . From the wide choice of possible matrix materials used in the preparation of controlled release formulations are , poly (ethylene oxides), methacrylic polymers, guar gum, xanthan gum, sodium alginate, chitosan, poly (acrylic acids), etc. Among the variety of hydrophilic polymers used, poly (ethylene oxides) (PEO) is one of the most important material used in the preparation of the matrix tablets because of its non-toxicity, high water-solubility and swellability.