• Journal of Pharmaceutical Investigation
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• v.19 no.1
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• pp.1-7
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• 1989

Coprecipitates of ibuprofen (IPF)-sodium deoxycholate (DC-Na) were prepared at various mixing ratios of IPF to DC-Na. X-ray diffraction measurments indicated that IPF in 1:3 and 1:5 IPF-DC-Na coprecipitate did not exist in the crystal form, however in the 1:8 coprecipitate, IPF remained its crystalline form. The dissolution rate was tested in pH 7.4 phosphate buffer by the paddle method of dissolution test of KP V. The dissolution rates of IPF from 1:1, 1:3, 1:5, 1:8 and 1:10(w/w) IPF-DC-Na coprecipitates and physical mixtures were compared with that of IPF alone. It was found that the dissolution rate of 1:5(w/w) coprecipitate was greater than that of pure IPF, coprecipitate and physical mixture at any other ratios of the two components. The concentration of IPF released from the IPF-DC-Na coprecipitates reached a plateau within 10 min, and thereafter gradually decreased indicating that IPF released from the coprecipitate was recrystallized due to the transient supersaturation.

• Journal of Pharmaceutical Investigation
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• v.18 no.2
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• pp.43-47
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• 1988

In order to increase the dissolution characteristics of relatively water-insoluble metoclopramide (MCP), coprecipitates of MCP with polyvinylpyrrolidone (PVP), polyethylene glycol (PEG) 1000, 4000 or 6000 were prepared in various drug to polymer ratios. The dissolution rate of MCP-PVP coprecipitate was greater than those of MCP alone, MCP-PVP physical mixture and MCP-PEG coprecipitates. The dissolution rate of MCP-PEG 6000 coprecipitate was greater than those of MCP-PEG 1000 and MCP-PEG 4000 coprecipitates. The dissolution half-lives $(T_{50%})$ for MCP alone and 1:5 (w/w) MCP-PEG 6000 coprecipitate were determined by the log-probit method at $37^{\circ}C$ and found to be 4.17 and 0.98 min, respectively.

• Journal of Pharmaceutical Investigation
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• v.15 no.3
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• pp.100-112
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• 1985

Dissolution characteristics of flurbiprofen solvent deposited on ${\alpha}-cyclodextrin$, ${\beta}-cyclodextrin$, lactose and corn starch were studied to evaluate the pharmaceutical aspects of solvent deposition method where drug was solvent deposited on the surface of excipients. In a solvent deposition system, the drug to excipient ratio and kind of excipient affect much on dissolution rates of flurbiprofen. The solvent deposition system formation was confirmed by scanning electron microscope. By increasing the amounts of matrix, it was possible to enhance the dissolution rate of flurbiprofen solvent deposition system. The amount of flurbiprofen dissolved from ${\beta}-cyclodextrin$ deposition system (1:10) at 60 minutes was enhanced 6.5 times in water and 28 times in simulated gastric juice compared with flurbiprofen alone. Flurbiprofen solvent deposited system (1:10) enhanced dissolution rate greater than inclusion complex and dispersion system.

• Journal of Mechanical Science and Technology
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• v.19 no.5
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• pp.1216-1225
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• 2005

$CO_{2}$ ocean sequestration is one of the promising options to reduce $CO_{2}$ concentration in the atmosphere because the ocean has vast capacity for $CO_{2}$ absorption. Therefore, in the present investigation, calculations for solubility and dissolution behavior of liquid $CO_{2}$ droplets released at 1000 m and 1500 m deep in the ocean from a moving ship and a fixed pipeline have been carried out in order to estimate the $CO_{2}$ dissolution characteristics in the ocean. The results show liquid $CO_{2}$ becomes bubble at around 500 m in depth, and the solubility of seawater is about $5{\%}$ less than of pure water. Also, it is shown that the injection of liquid from a moving ship is a more effective method for dissolution than from a fixed pipeline, and the presence of hydrate on liquid $CO_{2}$ acts as a resistant layer in dissolving liquid $CO_{2}$.

• Journal of Pharmaceutical Investigation
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• v.18 no.1
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• pp.23-30
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• 1988

The sustained-release micropellets containing rifampicin were prepared by spray congealing micropelleting technique using gelatin as the embedding matrix, and hardened by treating with the formalin-isopropanol mixture. Dissolution of rifampicin from micropellets was significantly retarded, and greatly dependent on formalin concentration, hardening time and pH of the dissolution medium. It was found that this prolongation was more distinguished in pH 1.2 dissolution medium rather than pH 7.4, which might be attributed to the swelling characteristics of gelatin used in the dissolution medium. In-vitro dissolution kinetics indicated that the drug release followed the first-order process.

• YAKHAK HOEJI
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• v.39 no.6
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• pp.593-599
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• 1995

Erythromycin was formulated as enteric-coated pellets in order to reduce degradation in stomach and gastromtestmal irritation, and to maximize the absorption in intestine followmg its oral administration. Core pellets were prepared using fluid-bed granulator with two different methods (powder layering and solvent spraying) and enteric-coated with two different coating polymers (HPMCP and Eudragit E30D). Physical characteristics md dissolution rates of core pellets and enteric-coated pellets were evaluated to optimize the formulation. Powder layering method resulted in shorter initial dissolution time than solvent spraying method, but physicochmical properties of the product were worse than solvent spraying method with respect to hardness, ftiability and density. The dissolution rate of the drug was increased with the addition of surfactants, showing concentration-dependence. The scanning electron microscopic observation of pellets revealed significant differences on the surface appearances prepared with solvent spraying method. The core pellet made with powder layering method had crystals on the surface, which resulted in poor physical properties of the pellets. The dissolution profiles of erythromycin pellets coated with HPMCP or Eudragit L30D were close to that of commercially available erythromycin enteric-coated product.

• Journal of Pharmaceutical Investigation
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• v.24 no.2
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• pp.57-65
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• 1994

To increase the dissolution rate of practically insoluble biphenyl dimethyl dicarboxylate (DDB), various solid dispersions were prepared with water soluble carriers, such as povidone (PVP K-30), poloxamer 407, sodium deoxycholate (SDC) and polyethylene glycol (PEG) 6000, at drug to carrier ratios of 1:3, 1:5 and 1:10 (w/w) by solvent or fusion method. Dissolution test was performed by the paddle method. The dissolution rate of DDB tablets (25 mg) on market was found to be very low (11.44, 9.02 and 6.42% at pH 1.2, 4.0 and 6.5 after 120 min, respectively). However, dissolution rates of DDB from various solid dispersions were very fast and reached supersaturation within 10 min. DDB-PEG 6000 solid dispersion appeared to be better in enhancing the in vitro dissolution rate than others. Furthermore, the incorporation of DDB and phosphatidylcholine (PC) into ${\beta}-cyclodextrin$ at ratios of 1:2:20, 1:5:20 and 1:10:20 resulted in a 4.9-, 11.2- and 19.6-fold increase in DDB dissolution after 120 min as compared with the pure drug, respectively. This might be attributed to the formation of lipid vesicles which entrapped a certain concentration of DDB during dissolution. On the other hand, the permeation of DDB through rabbit duodenal mucosa was examined using some enhancers such as SDC, sod. glycocholate (SGC) and glycyrrhizic acid ammonium salt (GAA). Only trace amounts of DDB were found to permeate through deuodenal mucosa in the absence of enhancer. SDC was found to markedly decrease the permeation flux of DDB, however, SGC and GAA (5 mM) enhanced the flux of DDB 1.6 and 2.4 times higher as compared with no additive, respectively.

• Journal of Pharmaceutical Investigation
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• v.40 no.3
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• pp.181-185
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• 2010

The objective of this study was to improve the extent of drug release as well as the dissolution rate of TD49, a novel algicidal agent, via the preparation of solid dispersion (SD). Among the various carriers tested, $Solutol^{(R)}$ HS15 was most effective to enhance the solubility of TD49. Subsequently, SDs of TD49 were prepared by using $Solutol^{(R)}$ HS15 and their solubility, dissolution characteristics and drug crystallinity were examined at various drug-carrier ratios. Solubili ty of TD49 was increased significantly in accordance with increasing the ratio of $Solutol^{(R)}$ HS15 in SDs. Compared to untreated powders and physical mixtures (PMs), SDs facilitated the faster and greater extent of drug release in water. Particularly, SD having the drug-carrier ratio of 1:20 exhibited approximately 90% of drug release within 1 hr. Differential scanning calorimetry (DSC) thermograms and X-ray diffraction (XRD) patterns suggested that SDs might enhance the dissolution of TD49 by changing the drug crystallinity to an amorphous form in addition to the increased solubilization of drug in the presence of $Solutol^{(R)}$ HS15. In conclusion, SD using $Solutol^{(R)}$ HS15 appeared to be effective to improve the extent of drug release and the dissolution rate of poorly water soluble TD49.

• Journal of Pharmaceutical Investigation
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• v.19 no.3
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• pp.155-161
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• 1989

Coprecipitates of chlorpropamide (CPA)-sodium deoxycholate (DC-Na) were prepared at various ratios of CPA to the DC-Na. The X-ray diffraction and DSC measurements indicated that CPA in 1:1 and 1:3 w/w CPA-DC-Na coprecipitates did not exist in amorphous form, but the others were amorphous. The dissolution rate of CPA from the CPA-DC-Na coprecipitates increased in distilled water and KP V 2nd disintegration test fluid (pH 6.8), but decreased extremely in KP V 1st disintegration test fluid (pH 1.2). The dissolution rates of CPA-DC-Na coprecipitates were compared with those of CPA alone and CPA-DC-Na physical mixtures. Especially, it was found that the dissolution rate of CPA markedly increased in the case of 1:5 CPA-DC-Na coprecipitate. The concentration of CPA dissolved from CPA-DC-Na coprecipitate reached a plateau within 5-10 min, and thereafter gradually decreased, indicating that CPA released from the coprecipitate was recrystallized.

• Resources Recycling
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• v.18 no.6
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• pp.38-45
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• 2009

Dissolution characteristics of magnesite ore in hydrochloric acid solution and removal of impurity were investigated. The dissolution yield increased with increasing temperature and with decreasing particle size. The optimum conditions for dissolution were found to be reaction period of 120 min, reaction temperature of $80^{\circ}C$ and mean particle size of 100. Under optimal dissolution condition the extraction of Mg was 98%. It was found that most of Si and Al exist in the residue, and they can be removed by filtering. Dissolved impurity ions were precipitated as metal hydroxides by pH adjustment. Polymers were used as coagulants for metal hydroxides and the suitable coagulant dosage was 1mg/100ml of non-ionic polymer.