Purpose:The aim of this work was to prepare nimodipine-loaded alginate-chitosan beads for sustained drug release. Methods: Nimodipine-loaded alginate-chitosan beads were prepared by ionic gelation method using various combinations of chitosan and Ca 2+ as cations and alginate as anion. The swelling ability and in vitro drug release characteristics of the beads were studied at pH 1.2 and 6.8. Infra-red (IR) spectrometry, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), x-ray diffraction (XRD), and atomic absorption spectroscopy (AAS) were also applied to investigate the physicochemical characteristics of the drug in bead formulations. Results: The surface morphology, size, and drug loading of the beads varied with increase in the concentration of chitosan and calcium chloride in the gelation medium. The swelling ability of the beads in different pH media was dependent on the presence of a polyelectrolyte complex in the beads and the pH of the media. Both calcium alginate beads and the beads treated with chitosan failed to release the drug at pH 1.2 over the period of study. On the other hand, at pH 6.8, calcium alginate beads released approx. 96 % of drug in 6 h, but treatment of the beads with chitosan lowered drug release to 73 %. Drug release mechanism was either "anomalous transport" or "case-II transport". Data from characterisation studies indicate that there was no significant change in the physical state of the drug in the bead formulations. Conclusion: Although nimodipine-loaded alginate beads showed poor sustained release characteristics, modification with chitosan yielded beads that exhibited sustained drug release.

The drug delivery systems using biodegradable natural polymeric particles are becoming a clinical reality with many benefits for the patient. The versatility of polymeric materials allows the fabrication of the delivery device with desirable degree of swelling, and drug release. Alginate is a natural biopolymer which forms a hydrogel in the presence of divalent cations like Ca 2ϩ . 1,2) The inert environment within the biopolymer network of alginates allows for the entrapment of a wide range of bioactive substances, cells and drug molecules, with minor interactions between them.3)The use of calcium-alginate beads in controlled drug delivery technology for the gastro-intestinal administration of proteins 4) and other drug molecules 5-7) are well known. Much attention has been received in recent years regarding the use of chitosan-alginate polyelectrolyte complex in controlled drug delivery. [8][9][10][11] The use of chitosan has been repeated in the literature is either for coating alginate beads in order to alter the diffusion rate of the encapsulated substances 12) or as an additive for the bulk modification of the beads structure. 13,14) Nateglinide is an antidiabetic drug used for the treatment of Type-II diabetes mellitus and has a short half-life of 1.5 h, and the usual oral dosage regimen is 60-240 mg taken 3 times a day. Thus Nateglinide is a suitable candidate for oral sustained release drug delivery. Keeping these in view, the present study has been undertaken. The investigation was phased out in the following manner. Firstly the effect of calcium ion and chitosan in the coagulation fluid on drug release characteristics and its mechanism was considered. Then the physical state of the drug in the beads and the swelling behavior of the bead formulations were undertaken. ExperimentalMaterials The following materials were obtained from the indicated suppliers and used as received: sodium alginate (low viscosity; viscosity of 2% solution 25°C, Ϸ250 cps from SNAP Natural and alginate products limited, Ranipet, India), chitosan (85% degree of deacetylation, molecular weight more than 10 3 kDa from India sea foods, Cochin, India). Calcium chloride dihydrate (Qualigens, Mumbai, India), di-sodium hydrogen phosphate anhydrous, potassium di-hydrogen phosphate, sodium acetate, potassium chloride, sodium hydroxide, dichloromethane, ethanol (99%), hydrochloric acid and acetic acid glacial (Merck, Mumbai, India). Nateglinide was of pharmaceutical grade (Alembic chemical works Ltd., Vadodara, India). Preparation of Nateglinide Loaded Calcium Alginate Beads (CAB)In this method the Nateglinide loaded calcium alginate beads were prepared using varying concentration of calcium chloride in the gelation medium [2% (w/v), 5% (w/v)] while maintaining the drug : polymer ratio as 1 : 3 and 1 : 4 separately for varying concentration of calcium chloride on each occasion. Required amount of Nateglinide dissolved in dichloromethane was slowly dispersed in sodium alginate solution with constant stirring for 3 h, maintaining the drug :...

Crystal modifications and dissolution rate of piroxicam Piroxicam is a nonsteroidal anti-inflammatory drug with low aqueous solubility which exhibits polymorphism. The present study was carried out to develop polymorphs of piroxicam with enhanced solubility and dissolution rate by the crystal modification technique using different solvent mixtures prepared with PEG 4000 and PVP K30. Physicochemical characteristics of the modified crystal forms of piroxicam were investigated by X-ray powder diffractometry, FT-IR spectrophotometry and differential scanning calorimetry. Dissolution and solubility profiles of each modified crystal form were studied and compared with pure piroxicam. Solvent evaporation method (method I) produced both needle and cubic shaped crystals. Slow crystallization from ethanol with addition of PEG 4000 or PVP K30 at room temperature (method II) produced cubic crystal forms. Needle forms produced by method I improved dissolution but not solubility. Cubic crystals produced by method I had a dissolution profile similar to that of untreated piroxicam but showed better solubility than untreated piroxicam. Cubic shaped crystals produced by method II showed improved dissolution, without a significant change in solubility. Based on the XRPD results, modified piroxicam crystals obtained by method I from acetone/benzene were cube shaped, which correlates well with the FTIR spectrum; modified needle forms obtained from ethanol/methanol and ethanol/acetone showed a slight shift of FTIR peak that may be attributed to differences in the internal structure or conformation.

Aim:The objective of the current study is to increase the dissolution rate of cefuroxime axetil (CA) by formation of binary CA solid dispersion using water soluble carriers such as polyvinylpyrrolidone (PVP K30) and polyethylene glycol (PEG 4000).Methods:Solid dispersions (SDs) between CA and PVP K30/PEG 4000 were formed by dissolving both compounds in a common solvent, methanol, which were rotary evaporated at 40°C for 12 h. Physical mixtures between CA and PVP K30/PEG 4000 were also formulated as to compare the efficiency of SDs. The physicochemical properties of CA and all its formulations were then characterized using differential scanning calorimetric analysis (DSC), powder X-ray diffraction studies (PXRD), and Fourier transform infrared spectroscopy (FTIR).Results:All SD formulations were found to have a higher dissolution rate comparatively to pure CA, while only physical mixtures of PVP K30 were found having a significantly higher dissolution rate. The enhancement of dissolution rate SD by PVP K30 may be caused by increase wettability, solubility, reduction in particle size or the formation of CA β crystalline. Increment of dissolution rate of CA SDs by PEG 4000 similarly may be caused by increase wettability, solubility, and reduction in particle size. This phenomenon may also be caused by amorphization as suggested by DSC and PXRD.Conclusions:The SD of CA with PVP K30 and PEG 4000, lends an ample credence for better therapeutic efficacy.

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