Objective:The objective of the present work was to formulate and to characterize controlled release matrix tablets of losartan potassium in order to improve bioavailability and to minimize the frequency of administration and increase the patient compliance.Materials and Methods:Losartan potassium controlled release matrix tablets were prepared by direct compression technique by the use of different natural, synthetic and semisynthetic polymers such as gum copal, gum acacia, hydroxypropyl methyl cellulose K100 (HPMC K100), eudragit RL 100 and carboxy methyl ethyl cellulose (CMEC) individually and also in combination. Studies were carried out to study the influence of type of polymer on drug release rate. All the formulations were subjected to physiochemical characterization such as weight variation, hardness, thickness, friability, drug content, and swelling index. In vitro dissolution studies were carried out simulated gastric fluid (pH 1.2) for first 2 h and followed by simulated intestinal fluid (pH 6.8) up to 24 h, and obtained dissolution data were fitted to in vitro release kinetic equations in order to know the order of kinetics and mechanism of drug release.Results and Discussion:Results of physiochemical characterization of losartan potassium matrix tablets were within acceptable limits. Formulation containing HPMC K100 and CMEC achieved the desired drug release profile up to 24 h followed zero order kinetics, release pattern dominated by Korsmeyer — Peppas model and mechanism of drug release by nonfickian diffusion. The good correlation obtained from Hixson-Crowell model indicates that changes in surface area of the tablet also influences the drug release.Conclusion:Based on the results, losartan potassium controlled release matrix tablets prepared by employing HPMC K100 and CMEC can attain the desired drug release up to 24 h, which results in maintaining steady state concentration and improving bioavailability.

The catalytic activity of binary oxides of Al2O3–Eu2O3, Al2O3–Sm2O3, Al2O3–Nd2O3, Al2O3–Pr6O11, and Al2O3–Y2O3 were checked in the transformations of α and β-pinene oxides. Al2O3–Eu2O3 and Al2O3–Nd2O3 are found to be best catalysts for α-pinene oxide isomeriztion. Among the oxiranes, α-pinene oxide showed more activity mainly yielding 2,2,3-trimethyl cyclopentene-1-acetaldehyde. β-pinene oxide produced trans-myrtanal and myrtanol.

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