• The Korean Journal of Pesticide Science
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• v.9 no.3
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• pp.243-249
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• 2005

The chemical and toxicological studies were conducted with acetamiprid 2% granules including different controlling agents for development of controlled-release acetamiprid 2% granule. The fundamental formulation recipe of acetamiprid 2% granule was prepared by the insoluble matrix using polyethylene wax. Starch, cellulose and mineral (calcium carbonate) were used as controlling agents. As a result of studies, release rate of active ingredient from granules into water static condition at $25^{\circ}C$ was increased by addition of starch and cellulose, but was decreased by addition of calcium carbonate. We could select calcium carbonate as controlling agent and make three granules which there were difference in release profiles of active ingredient according to contents of polyethylene wax. 24 hours-release rates of acetamiprid from three granules into water static condition at $25^{\circ}C$ were respectively 75, 50 and 25% when contents of wax were 2, 10 and 20%. The granule which 24 hours-release rate was 25% showed lower acute toxicity against mice and rats.

• Polymer(Korea)
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• v.29 no.5
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• pp.468-474
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• 2005

PLGA and PCL copolymers initiated by carbitol as drug carriers were synthesized by ring-opening polymerization of L-lactide (LA), glycolide (GA), and $\varepsilon-caprolactone(\varepsilon-CL)$. Implantable wafers were simply fabricated by direct compression method after physical mixing of copolymers and bovine serum albumin-fluorescein isothiocyanate (BSA-FITC) as a model protein drug. The release amounts of BSA-FITC from wafers were determined by fluorescence intensity using the fluorescence spectrophotometer. Also, the release behavior of BSA-FITC on wafers was controlled by adding the additives such as collagen, small intestinal submucosa (SIS), poly(vinyl pyrrolidone) (PVP), and poly(thylene glycol) (PEG). The wafer prepared by PLGA and PCL exhibited slow release within $10\%$ for 30 days. But, those prepared by a variety of additives exhibited the controlled BSA release patterns with a dependence on the additive contents. furthermore, the wafers containing natural materials such as collagen and SIS showed more zero-order release profile than that with synthetic materials such as PVP and PEG. It was confirmed that the release of BSA from implantable wafers could be easily controlled by adding natural additives.

• Restorative Dentistry and Endodontics
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• v.29 no.6
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• pp.548-552
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• 2004

Intracanal disinfection of infected root canal is one of important treatment procedure. This in vitro study aimed to evaluate whether the surface polymers of controlled release drug (CRD) can effectively control the release rate of chlorhexidine for root canal disinfection. Four CRD prototypes were prepared: Group A (n=12); The core device (absorbent paper point) was loaded with 40% CHX solution as control. Group B (n=12); same as group A, but the device was coated with chitosan. Group C (n=12); same as group A and then coated three times with 5% PMMA. Group D (n=12); same as group A and then coated three times with 3% PLGA. All CRD prototypes were soaked in 3 mL distilled water for experimental periods and the concentrations of released CHX from each CRD prototype were determined using a UV spectrophotometer. Results showed that release rate of CHX were the greatest in the non-coated group (control group), followed by the chitosan-coated group, the PLGA-coated group, and the PMMA-coated group (P < 0.05). This data indicate that surface polymers can control the release rate of CHX from the CRD prototypes.

• Journal of Pharmaceutical Investigation
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• v.20 no.1
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• pp.13-18
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• 1990

Hydrocortisone (HC) sustained-release suppositories were prepared by using a solid matrix of methacrylic acid-methacrylic acid methyl ester copolymer $(Eudragit\;L_{100}^{R}:\;EL)$ as a poorly water soluble carrier and polyethylene glycole 1540 (PEG) as an water soluble carrier. HC release rate was controlled by complexation with ${\beta}-cyclodextrin$ $({\beta}-CyD)$ which was confirmed by X-ray diffractometry, IR-spectroscopy and differential scanning calorimetry. Release rate of HC from the EL-PEG matrix suppositories decreased with increase of EL contents. The release rale from $HC-{\beta}-CyD$ complex decreased in the following order: $HC-{\beta}-CyD/PEG$ > HC/PEG > $HC-{\beta}-CyD/EL_{10%}-PEG$ > $HC/EL_{10%}-PEG$ > $HC-{\beta}-CyD/EL_{15%}-PEG$ > $HC/EL_{15%}-PEG$ > $HC-{\beta}-CyD/EL_{20%}-PEG$ > $HC/EL_{20%}-PEG$. The crystallinity of HC in polymer matrix was identified using X-ray diffractometer and the surface of matrix suppositories after release test was examined by scanning electron microscopy. The sustained release of HC from these matrix suppositories was attributed to the network structure of EL.

• Macromolecular Research
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• v.11 no.4
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• pp.283-290
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• 2003

Organic drugs including aspirin, omeprazole, and naproxen with three different levels of octanol/water partition coefficient were examined for their release behavior from the amphiphilic PCL-b-PEO-b-PCL (PCEC) matrix. Scanning electron micrograph (SEM) of PCEC illustrated a well defined two-phase morphology consisted of dispersed poly(ethylene oxide) (PEO) domain and continuous polycaprolactone (PCL) phase. Differential scanning calorimetry (DSC) and X-ray diffractometry (XRD) experiments veri tied that three model drugs are dissolved as a molecular dispersion in PCEC matrix. The release of hydrophilic aspirin closely followed the water absorption profile of the matrix indicating that its major fraction is present in PEO domain. However, substantial amount of aspirin present in less hydrophilic region displayed discontinuous biphasic release pattern. In the case of omeprazole with intermediate hydrophobicity consistent release behavior was observed for a period of 24 hrs after the rapid liberation of ca. 10% of the drug presumably partitioned in PEO phase. It was ascribed to the fact that the progressive hydration of PCEC matrix gradually increased the chance of drug/water exposure to compensate the exhaustion of device. Naproxen with the highest octanol/water distribution coefficient among three model drugs exhibited a limited release of 35% for 24 hrs. Finally, hydroxypropyl methylcellulose phthalate (HPMCP)/PCEC blend matrix demonstrated an accelerated and quantitative release of hydrophobic naproxen by generating high porosity and thereby expanding polymer/water interface.

• Fisheries and Aquatic Sciences
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• v.14 no.4
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• pp.379-388
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• 2011

The mechanism by which gonadotropin-releasing hormone (GnRH) and dopamine (DA) control gonadotropin (GTH) release was studied in male and female rainbow trout using cultured pituitary cells obtained at different reproductive stages. The mechanisms of follicle-stimulating hormone (FSH) release by GnRH and DA could not be determined yet. However, basal and salmon-type GnRH (sGnRH)- or chicken-II-type GnRH (cGnRH-II)- induced luteinizing hormone (LH) release increased with gonadal maturation in both sexes. LH release activity was higher after sGnRH stimulation than cGnRH-II stimulation at maturing stages in both sexes. The GnRH antagonist ([Ac-3, 4-dehydro-$Pro^1$, D-p-F-$Phe^2$, D-$Trp^{3,6}$] GnRH) suppressed LH release by sGnRH stimulation in a dose-dependent manner, although the effect was weak in maturing fish. The role of DA as a GTH-release inhibitory factor differs during the reproductive cycle: the inhibition of sGnRH-stimulated LH release by DA was stronger in immature fish than in maturing, ovulating, or spermiated fish. DA did not completely inhibit sGnRH-stimulated LH release, and DA alone did not alter basal LH release. Relatively high doses ($10^{-6}$ or $10^{-5}M$) of domperidone (DOM, a DA D2 antagonist) increased LH release, which did not change with reproductive stage in either sex. The potency of DOM to enhance sGnRH-stimulated LH release was higher in maturing and ovulated fish than in immature fish. These data suggest that LH release from the pituitary gland is controlled by dual neuroendocrine mechanisms by GnRH and DA in rainbow trout, as has been reported in other teleosts. The mechanism of control of FSH release, however, remains unknown.

• Journal of Pharmaceutical Investigation
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• v.31 no.2
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• pp.101-106
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• 2001

Alginate-chitosan (anion-cationic polymeric complex) was prepared to control the release rate of silver sulfadiazine (AgSD). Na-alginate (2%) solution containing AgSD was gelled in $CaCl_2$ solution. The gel beads formed were immediately encapsulated with chitosan (CS). The gel matrix and membrane were then reinforced with chondroitin-6-sulfate (Ch6S). Release rate of AgSD from the gel matrix was investigated by placing alginate beads in the sac of cellulose membrane simmered in HEPES-buffer solution. The concentration of AgSD released was analyzed by UV at 264 nm. Incorporation capacity of AgSD in Ca-alginate gel was more than 90%. Alginate-Ch6S-CS could control the release rate of AgSD. The amount of AgSD release was dependent on the AgSD loading dose. Incorporation of tripolyphosphate (polyanionic crosslinker) onto the alginate-Ch6S-CS bead increased the release rate of AgSD. Collagen-coating had no influence on the AgSD release rate. Alginate-Ch6S-CS beads with a sufficiently high AgSD encapsulation were capable of controlling the release of the drug over 10 days. In summary, alginate-Ch6S-CS beads could be used as a sustained delivery for AgSD and provide local targeting with low silver toxicity and patient discomfort.

• Journal of Pharmaceutical Investigation
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• v.35 no.3
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• pp.157-163
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• 2005

The pellets with multiple drug release system (MDRS) of Diltiazem. HCl which consist of immediate drug release layer, drug reservoir layer and controlled release rate membrane, were prepared by using CF-Coater. As main factors for more effective MDRS of Diltiazem. HCl, ethylcellulose was used for the controlling drug release rate, and diethylphthalate was used for plasticizer, respectively. In vitro evaluation study was performed by comparative dissolution test between our test MDRS and reference Diltiazem. HCl preparation. The physical tests were performed using FT-IR and SEM. In vivo evaluation was also performed by observing the behavior of a plasma drug concentration after oral administration. The bioavailability was determined by analyzing the blood sample after oral administration to healthy, male volunteers once a day. As a result, there were no significant differences in bioequivalence parameters $(AUC_{\infty},\;C_{max},\;t_{1/2})$ between two systems. It might be concluded that our MDRS of Diltiazem. HCl could be an alternative delivery system to reference drug preparation.

• Journal of Pharmaceutical Investigation
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• v.28 no.2
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• pp.109-113
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• 1998

This study is purposed to develop the sustained release and bioavailability of piracetam (PA). The use of alginate beads as a means to achieve sustained release of piracetam was evaluated in comparison with that of piracetam alone. In the PA-sodium alginate(SA) beads was confirmed by differential scanning calorimetry thermogram(DSC), indicating a relative shift of an endometric peak of PA to higher temperature. The changes in dissolution rates from PA-SA beads and PASA beads coated by chitosan(CHO) were significantly slower than that of intact PA. The release rate of PA-SA in the gastric fluid was markedly decreased compared with that in the intestinal fluid, suggesting that PA is mostly released in the intestinal fluid. However, the PA/SA ratio scarcely affected the release profile. The blood concentration- time curves of PA, PA-SA and PA-SA-CHO were obtained by oral administration to rats. $T_{max}$ of PA, PA-SA and PA-SA-CHO were 1, 10 and 6 hours, respectively. It was confirmed that the release of PA was prolonged by the formulation of PA-SA beads and PA-SA-CHO beads.

• Macromolecular Research
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• v.8 no.6
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• pp.253-260
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• 2000

Biodegradable wafers were prepared with poly (hydroxybutyrate-co-hydroxyvalerate) (PHBV;5, 10, and 15 mole% for 3-hydroxyvalerate) by simple heat pressing method for the sustained release of antibiotic agent, gentamicin sulfate (GS) to investigate the possibility of the treatment for osteomyelitis. The effects of hydroxyvalerate (HV) content, thickness of wafers, various types of additives such as sodium dodecyl sulfate (SDS), microcrystalline cellulose, polyvinylpyrrolidone, and hydroxypropylcellulose (HPC), and different initial drug loading ratio on the release profile have been investigated. In vitro release studies showed that different release patterns and rates could be achieved by simply modifying factors in the preparation conditions. PHBV wafers with 3 mm thickness, 10% of GS initial loading, 15% of HV content and addition of 5% of SDS and HPC were free from initial burst and a near-zero-order sustained release was observed for over 30 days. It might be suggested that the mechanisms of G5 release may be more predominant simple dissolution and diffusion of GS than erosion of PHBV in our system.