• YAKHAK HOEJI
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• v.20 no.1
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• pp.63-69
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• 1976

Prednisolone tablet product design problem was structured as constrained optimization problem and subsequently solved by multiple regression analysis and Lagrangian method of optimixation. Prednisolone was the drug chosen and anhydrous lactose and corn starch were the adjuvants. The effect of anhydrous lactose and corn starch concentrations on tablet hardness, volume, disintegration time and in vitro release rate was studied. The concentrations of anhydrous lactose and corn starch used in this experiment were 30-60 percent and 5-30 percent, respectively. A full second-order (quadratic) model with all possible two-factor interactions was employed. To obtain the values of anhydrous lactose and corn starch which miniumize the in vitro : release time (t$_{60%}$) subject to the constraint on tablet hardness, disintegration time and volume, we solved the Lagrange function. Multiple correlation coefficients for the regression models were correlated at less than 0.05 level and it was found that the optimum concentrations of anhydrous lactose and corn starch were 45 percent and 21 percent, respectively.

• YAKHAK HOEJI
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• v.39 no.1
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• pp.48-54
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• 1995

Coupling of tetracycline(Tc) to dithiocarbamate chitosan(DTCC) via chelate bond was investigated varying reaction time, concentration, temperature, pH, and Ca(II)/Tc ratio. The amount of Tc bound to matrix increased to give a maximum and decreased as the reaction proceeded. The degree and rate of dissociation of Tc complex were affected by the reaction temperature, and pH. By running the reaction at low temperature and pH, the degree of dissociation was greatly diminished. Properties of drug-release from DTCC-Ca(II)-Tc complex were studied by batch- and flow-method and release of Tc and CA(II) by flow method followed nearly zero-order. DTCC-Ca(II)-Tc showed very prolonged antimicrobial activity compared to that of free Tc.

• Polymer(Korea)
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• v.36 no.2
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• pp.163-168
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• 2012

Recently, along with technology development of endoscopic equipment, the stent technology has been developed for the convenience of operation, shortening of recovery times, and reduction of patient's pain. In this study, paclitaxel-eluting metal stents for treatment of biliary benign stenosis were developed through an electrospray-coating method. Polyether-based polyurethane (PELLETHANE 2363-80AE$^{(R)}$)) and paclitaxel were coated onto the surface of a metallic stent and Pluronic F127 was used as an additive. As a result, physicochemical characterization of paclitaxel via SEM, FTIR, contact angle and XRD techniques revealed the information of solid state of paclitaxel-loaded PU film. The in vitro release profile showed a slower release rate with a higher content of paclitaxel.

• Journal of Biomedical Engineering Research
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• v.39 no.1
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• pp.30-35
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• 2018

Conventional drug delivery methods mainly include subcutaneous injection and oral administration. Subcutaneous injection has the advantages of delivering the correct concentration, but it might cause pain and trauma to patients. Although oral administrations do not accompany pain as the subcutaneous injection, unexpected side effects may occur because they undergo digestion process and it is not easy for many drugs to be exposed to targeted sites with proper concentration. While dissolving microneedles have been extensively studied to overcome the limitations of conventional subcutaneous injection, the effects on microneedle shapes for drug release have not been fully explored. In this study, the characteristics of hyaluronic acid microneedles for cone and quadrangular pyramidal shapes were examined by the size, volume, contact surface area, skin permeability, and dissolution rate. As a result, the cone shapes of hyaluronic acid microneedles had high skin permeability, and the quadrangular pyramid of shapes hyaluronic acid microneedles showed a fast dissolution rate, given by the large contact area on the skin. Based on the results, we could confirm that the shape of a dissolving microneedles can affect skin permeability and the drug delivery rate.

• YAKHAK HOEJI
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• v.35 no.2
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• pp.111-118
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• 1991

A comparative study was performed on two different strains of Leishmania major, chloroquine sensitive strains (Chl$^{S}$) and its mutant chloroquine resistant strains (Chl$^{R}$). Chl$^{R}$ strains were obtained at 5$\times$$10^{-4}$M chloroquine. Remarkable differences were observed at the initial chloroquine uptake in Chl$^{R}$ and Chl$^{S}$, i.e., the rate of uptake was very reduced in Chl$^{R}$ (Km values were 70 nM and 125 nM, respectively). Influx and accumulation of chloroquine were also compared between wild type and mutant. An increasing tendency in both influx and accumulation of chloroquine was shown in Chl$^{S}$, but Chl$^{R}$ demonstrated a rapid release after a little uptake (influx) at the early stage. This result is thought to be basis of their resistance for Chl$^{R}$ strains.

• Journal of Pharmaceutical Investigation
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• v.22 no.1
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• pp.23-31
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• 1992

A novel O-diethylaminoethyl chitosan (DEAE-chitosan) was synthesized via Schiff's reaction between chitosan and benzaldehyde. $C_2$ amino group was protected via Schiffs base reaction with benzaldehyde to form N-benzylidene chitosan. After reaction with diethylaminoethyl chloride, Schiffs base was removed by reacting O-diethylaminothyl-N-benzylidene chitosan and hydrochloric acid. Tensile strength of DEAE-chitosan was improved due to the incorporation of bulky side group in $C_6$ position of chitosan. DEAE-chitosan showed a pH-dependent swelling characteristics. Release rate of riboflavin was dependent on the water content of DEAE-chitosan that is a function of crosslinking degrees.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.506-512
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• 2017

The purpose of this study was to improve release rate and bioavailability of nateglinide formulation. Polymorphism selection and particle size control were performed to enhance formulation dissolution rate, and a pH modifier was included in the formulation to overcome pH-dependent solubility of nateglinide. The enhanced dissolution rate was characterized by using a dissolution test. The results showed that H-type raw material had a higher dissolution rate than that of B-type raw material. There was 6.2% difference in dissolution between the two materials at 60 min. With regard to particle size, raw material with a $1.13{\mu}m$ particle size showed a 20% faster release rate than that of raw material with a $2.28{\mu}m$ particle size. Furthermore, fumaric acid was included in formulation as a pH modifier. That addition produced a greater than 50% improvement in dissolution rate. In conclusion, dissolution rate of nateglinide can be enhanced by optimizing its polymorphism and particle size; moreover, a synergistic effect on the enhancement of dissolution rate is obtained by including fumaric acid, a pH modifier, in the formulation.

• Journal of Pharmaceutical Investigation
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• v.29 no.2
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• pp.93-98
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• 1999

Semi-solid poly(ortho esters) (POE) were prepared to provide bioerodible carriers for sustained drug delivery systems of nifedipine in the treatment of cardiovascular disease. As the POE has viscous behavior at room temperature, a significant advantage of this polymer is that it can be injected without any surgical intervention. The POE was synthesized by a transesterification reaction between 1,2,6-hexanetriol and trimethyl orthoacetate and the nifedipine release from POE was studied in vitro. The release rate of nifedipine decreased with increasing the amount of nifedipine and the diethanolamine dispersed in the polymer. But the excess amounts, above 3%, of diethanolamine retarded the release of nifedipine. In vivo biocompatibility studies were carried out in rats with nifedipine loaded POE. Histopathological analysis showed that nifedipine loaded POE implants were well-tolerated by rats when used subcutaneously. In case of the rats implanted POE containing diethanolamine, tissue necrosis and inflammation were occured. Pharmacokinetic studies of nifedipine loaded POE implants were carried out in rabbits. In all cases, plasma concentrations of nifedipine were maintained over 15 ng/ml for at least 360 hours and biological half $life(t_{1/2})$ and mean residence time(MRT) were increased by addition of diethanolamine.

• Journal of Pharmaceutical Investigation
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• v.25 no.3
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• pp.43-51
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• 1995

The in vitro skin permeability of 16 drugs with a wide span of lipophilicity (log P ranging from -0,95 to 4.40) was evaluated with an ethanol/panasate 800 (tricaprylin, P-800) (40/60) lipophilic binary vehicle and an ethanol/water (60/40) hydrophilic binary vehicle with lauric acid, The skin permeability of the drugs was enhanced by the use of the ethanol/P-800 (40/60) binary vehicle or the ethanol/water (60/40) binary vehicle with lauric acid; permeation rate was increased and lag time' was decreased. The relationship between lipophilicity and skin permeation rate of the drugs showed parabolic shapes with their peaks at much greater hydrophilic range compared with other past references. In the in vivo skin absorption of theophylline using abdominal rat skin, the ethanol/P-800 (40/60)-7% (w/w) ethycellulose gel produced a good feature as a sustained-release preparation, and the ethanol/water (60/40)-3 % (w/w) HPMC gel with lauric acid showed the highest BA value. The results suggest that the lipophilicity of a drug is a main factor for prediction of the skin permeability of the drug and that the ethanol/P-800 (40/60) binary vehicle and ethanol/water (60/40) binary vehicle with lauric acid would be good candidates for clinical transdermal application of hydrophilic drugs.

• Membrane Journal
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• v.18 no.2
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• pp.124-131
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• 2008

The biodegradable hyaluronic acid membranes cross-linked with lactide using the crosslinking agent, 1,3-butadiene diepoxide (BD), were prepared as a potential biocompatible material for tissue engineering. The degree of lactide and BD reaction of the crosslinked membrane was determined by the analysis of nuclear magnetic resonance spectroscopy 6% of growth inhibition was observed in case of high BD concentration but the value is low enough not to affect cell growth. As the crosslinking reaction temperature increased, elongation increased and swelling ratio decreased. The rate of degradation was found to increase with the crosslinking temperature. The drug release experiment showed that the transport of drug through the membrane decreased with the crosslinking temperature.