Nimesulide belongs to the group of semi-selective COX-2 inhibitors, widely used in solid oral formulations. In the present work the influence of surfactants among other drug excipients, as well as particle size of the active substance and the effects of medium pH on the dissolution rate of nimesulide from solid pharmaceutical forms. For that purpose, four different preparations containing 100 mg nimesulide per tablet and available in the market of Bosnia and Herzegovina (labeled here as A, B, C and D) were studied. The test for the assessment of dissolution profiles of the formulations was performed in surfactant-free dissolution medium pH 7.5. The dissolution profiles were compared by calculating difference (f1), and similarity (f2) factors. The increasing dissolution medium pH value from 7.5 to 7.75 resulted in a significant increase of nimesulide dissolution rate from the examined formulations. Also, the results showed that particle size affects to a great extent the dissolution rate and the best results were achieved with micronized nimesulide. The presence of the surfactants among the other excipients expressed a negligible effect on the dissolution profile.

Today, research has largely focused on examining impurities in pharmaceutical compounds and monitoring the stability of drug substances in pharmaceutical formulations in a given time interval. Recently, emphasis has been placed on impurities, especially degradation products and their limits within specifications. Stress testing/accelerated storage conditions testing can assist in the identification of potential degradation products. This type of testing should include effects of temperature and humidity. In this research, stability of nimesulide tablets from five different manufacturers was tested by using accelerated storage conditions, in which samples were stored in a chamber under the following conditions: temperature 40oC ± 2oC and relative humidity 75 % ± 5 %. The content of nimesulide and impurities formed as a consequence of its degradation was observed within precisely defined time intervals (0,3 and 6 months) by using RP-HPLC method. Test results indicate the appropriate stability of nimesulide in all analyzed tablets. Content of nimesulide ranged between 95,38% - 104,45% of the Recovery value, whilst individual and total impurities were within acceptable limits. It is also worth noting appearance of 3 unknown impurities which are detected in all analyzed products after the period of 6 months at the following relative retention times: 1,75, 2,08 and 2,97.

The optimal solution of the weakly coupled algebraic discrete Riccati equation is obtained in terms of a reduced-order continuous-type algebraic Riccati equation via the use of a bilinear transformation. The proposed method has a rate of convergence of O( epsilon /sup 2/) where epsilon represents a small coupling parameter. A real-world physical example (a chemical plant model) demonstrates the efficiency of the proposed method. Simulation results obtained using a package for a computer-aided control system are presented. For this specific real-world example, the algorithm perfectly matches the presented theory, since convergence, with an accuracy of 10/sup -4/, is achieved after nine iterations (i.e., 0.68/sup 18/=10/sup -4/). >