Losartan potassium microcapsule from a batch was taken at random and was crushed to a fine powder. The powdered material was transferred into a 100 ml volumetric flask and 70 ml of 6.8 pH phosphate buffer was added to it. It was shaken occasionally for about 30 min and the volume was made up to 100 ml by adding 6.8 pH phosphate buffer. About 10 ml of the solution from the volumetric flask was this website taken and centrifuged. The supernatant solution from the centrifuge tube was collected and again filtered by using Millipore

filter. Then the filtrate was subsequently diluted and the absorbance was measured at 254 nm. This test was repeated six times (N = 6) for each batch of microcapsules. Based on the dissolution studies performed on all the microcapsules, some of the optimized formulation were selected and further investigation by SEM analysis, DSC and FTIR spectral studies. Dissolution rate studies for each batch of microcapsules were performed in a calibrated 8 station dissolution

test apparatus (LABINDIA DS 8000), equipped with paddles (USP apparatus II method) employing 900 ml of 6.8 pH phosphate buffer as dissolution medium.11 Samples were withdrawn at regular intervals up to 16 h. Fresh volume of the medium was replaced with the withdrawn volume to maintain constant volume throughout the experiment. Samples withdrawn were suitably diluted with same dissolution medium and the amount of drug released was estimated by ELICO double beam spectrophotometer at 254 nm GSK2656157 order based on the various dissolution parameters were calculated with the following, first order, Higuchi and Koresmeyer Peppa’s equation respectively. The dissolution profiles of various microcapsules were shown as Fig. 1. The dissolution parameters evaluated were given in Table 3. The samples were coated with a thin gold layer by sputter coater unit (SPI, Sputter, USA). Then, the SEM photographs were taken by a scanning electron microscope (scanning electron microscope JSM-6390, Japan) operated at an accelerated

voltage of 5 KV. A differential scanning calorimeter (DSC 60, Shimadzu) was used to obtain the DSC curves of LP by solvent evaporation. About 10 mg of sample was weighed in a standard open aluminium pans, were scanned from 20 to 300 °C, at a heating rate of 10 °C/min while being purged with dry nitrogen. out I.R spectral studies were carried out on some selected microcapsules by using BRUKER FTIR. These studies on microcapsules were performed before they are subjected to dissolution studies to check the structural variation if any arised between the drug and excipients used. In the present investigation losartan potassium microcapsules were prepared by solvent evaporation technique. Eudragit S100 was used as controlled release coating polymeric material for the preparation of microcapsules. Methanol and acetone at 1:1 ratio was used as solvent for dissolving Eudragit S100 and losartan potassium.