• Journal of Pharmaceutical Investigation
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• v.22 no.4
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• pp.267-279
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• 1992

Microencapsulations of amoxicillin and cephalexin, using Eudragit RS, RL, E, S and L were investigated. The microcapsules were prepared by the solvent evaporation process in liquid paraffin phase, which is based on dispersion of acetone/isopropanol containing the drug in liquid paraffin. Aluminium tristearate was used as an additive for the preparation of microcapsules. The size distribution, dissolution test and observation by SEM were examined. Good reproducibility in microcapsule preparation was observed. The microcapsules obtained were spherical and free-flowing particles. The dissolution rates of amoxicillin and cephalexin from the microcapsules were considerably decreased as compared with those from amoxicillin and cephalexin powder, respectively. As the dispersing agents (aluminium tristearate) increased, the particle size of microcapsules decreased and the dissolution rate increased. In order to control the release rate of drugs, microcapsules were prepared by mixing Eudragit RS/RL or Eudragit S/L. As Eudragit RL ratio in microcapsule of Eudragit RS/RL increased, the dissolution rate increased. As Eudragit L ratio in microcapsule of Eudragit S/L increased, the dissolution rate increased. Furthermore, the release rates of drugs from Eudragit RS/L or RS/polyelthylene glycol 1540 (PEG 1540) were examined. The dissolution rate of drugs increased with increasing of Eudragit L or PEG 1540 ratio. In conclusion, the release rates of drugs from Eudragit RS/RL or RS/PEG 1540 microcapsule could be controlled, and these microcapsules will be convenient for reducing frequency of administration.

• Journal of Pharmaceutical Investigation
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• v.18 no.4
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• pp.175-180
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• 1988

The role and effect of aluminum tristearate in microencapsulation were investigated based on the dispersion system of ethambutol hydrochloride in acetone-liquid paraffin. Eudragit RS was used as a wall-forming material. Eudragit RS microcapsules prepared using aluminum tristearate were uniform, free-flowing particles. The phase diagram of ethambutol hydrochloride-Eudragit RS-aluminum tristearate indicated that spherical microcapsules ranging from 250 to 1400 ${\mu}m$ in diameter could be prepared only in a very limited region. Instrumental analysis using an energy dispersive-type X-ray microanalyser and a scanning electron microscope showed that aluminum tristearate was localized near the surface of microcapsules. From these results, it was presumed that aluminum tristearate reduced the phase tension between Eudragit microcapsules and liquid paraffin. The dissolution rates of ethambutol hydrochloride from Eudragit RS microcapsules were consideraly lower than those from ethambutol hydrochloride powders and decreased as the amount of aluminum tristearate decreased.

• Archives of Pharmacal Research
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• v.16 no.1
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• pp.50-56
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• 1993

The microencapsulation of sodium naproxen with Eudragit. RS was studied by coacrtvation/phase separation process using Span 80 in mineral oil/acetone system. Various factors which affect the mciroencapsulation, e.g., stirring speed, and surfactant concentraction, Eudagit RS concentration and loading drug amounts were examined. For the evaluation of the prepared microcapsules, release rate, particle size distribution and surface appearance as well as in vivo test were carried out. The addition of n-hexane and freezing of microcapsules accelerated the hardening of microcapsules. The optimum concentration of Span 80 ti prepare the smallest microcapsules was the same value with the CMC of Span 80 in solvent system. When 1.5% (w/w) Span 80 was used, the smallest microcapsules were formed $(30.02\pm5.05\mu$ in diameter) belonging to the powder category showing smooth, round and uniform surface. The release of sodium naproxen was retarded by microencapsulation with Eudragit RS. The Eudragit RS microcapsules showed significantly increased AUC and MRT and deceased Cl/F in rabbits.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1993.04a
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• pp.102-102
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• 1993

제1차년도 연구에서 Goto등의 방법을 응용하여 생체에 대하여 안전하고 transit 양상에 대해 재현성이 확보되는 경구용 방출조절성 마이크로캅셀을 개발 하였다. 즉 methacrylate polymer(Eudragit RS, RL, E, S 및 L)의 특성을 이용하여 B-락탑계 항생물질(amoxicillin 및 cephaiexin)을 함유하는 마이크로캅셀을 제조하는 방법을 개발하였다. 본 연구에 있어서는 제1차년도에 in vitro 실험결과 유용한 서방성 제제로 판단되는 cephalexin 함유 Eudragit RS/RL, S/L 및 RS/PEG 마이크로캅셀을 제조하여 가토에 경구투여 후 생체이용률을 평가하였다. 또한 소화관에서 약물의 방출속도 및 흡수속도등을 고려한 모델을 구축하여 약물속도론적으로 해석함으로써 실제 임상에 적용할 수 있는 유용한 경구투여용 마이크로캅셀을 개발하고자 하였다. 1. in vitro 실험 입도분포, 함량시험, 용출시험 2. in vivo 실험 1) AUC에 의한 평가 2) Vallver 등의 방법에 의한 평가 3) 약물속도론적 방법에 의한 평가 결론: 1. Eudragit 의 특성을 이용하여 유중건조법으로 40％ cephalexin 함유 Eudragit RL/RS, S/L 및 RS/PEG 마이크로캅셀을 제조할 수 있었고 각 조성비를 변화시킴으로써 약물방출을 조절할 수 있었다. 2. 약물속도론적 해석결과 마이크로캅셀제제의 Ka는 변화하지않고 Kr이 감소되는 즉, 약물흡수의 율속단계가 방출단계임을 보여주었다. 3. Eudragit RL/RS 마이크로캅셀은 제어방출 효율 및 흡수속도 효율이 우수한 서방성 제형으로 평가되었다.

• Polymer(Korea)
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• v.31 no.4
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• pp.329-334
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• 2007

Osmotic pellet system, which is one of the oral drug delivery systems, has been developed to improve manufacturing process, reduce product cost and other problems of osmotic tablet systems. Osmotic pellet is consisted of water swellable seed layer, drug layer, and membrane layer. Among them, the membrane layer plays an important role in a control of the drug release. In this work, we examined the effect of ratio for Eudragit RL and RS on the drug release behavior. Osmotic pellet with nifedipine as a model drug was easily obtained in a good yield by fluidized bed coater. Osmotic pellet showed round morphology with a range of size $1300{\sim}1500\;{\mu}m$. In the experiment of nifedipine release, the release amount increased with the increase of the ratio of Eudragit. This is due to the fact that Eudragit RL contains more hydrophilic quaternary ammonium group than Eudragit RS. Additionally, the release amount was retarded with increasing the membrane thickness. There are no differences in the release amount measured at the different pH 1.2, 6.5, 6.8, and 7.2. In conclusion, it was found that the drug release from osmotic pellets depended on the composition ratio and coating thickness of membrane layer.

• Journal of Pharmaceutical Investigation
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• v.23 no.2
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• pp.103-110
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• 1993

Microcapsules(Mc) of cephalexin (CEPH), using Eudragit RS, RL, L, S and polyethylene glycol 1540, were evaluated biopharmaceutically. The area under the curve of CEPH-Eudragit RS/RL Mc administered orally once was larger than that of cephalexin powder twice every 6 hrs. Controlledrelease effectiveness and the absorption rate effectiveness, two important parameters of Vallner's method, of CEPH-Eudragit RS/RL Mc indicate that these Mc can be good sustained-release preparations. And a simple pharmacokinetic model is introduced which allows the gastric emptying and intestinal-transit rates of a drug itself and a solid-state drug contained in Mc. Decreasing $K_r$, without change in $K_a$, showed that the rate-limiting step of absorption moved from absorption step to releasestep.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.409.3-410
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• 2002

Microencapsulations of piroxicam using the mixture of Eudragit RS with RL or Eudragit L or E or S according to Eudragit RS were carried out. The Eudragit microspheres of piroxicam were prepared by solvent method. Piroxicam and Eudragit polymer were dissoved in methylene chloride and dispersed in 0.5% pOlyvinyl alcohol solution and solvent evaporated. The average diameters of various Eudragit microspheres were from 40 to 43${\mu}{\textrm}{m}$. A good and smooth surface of microspheres observed by SEM were shown in all type of microspheres. (omitted)

• Archives of Pharmacal Research
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• v.19 no.1
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• pp.1-5
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• 1996

Laminated films composed of drug-containing reservoir layer and drug-free membrane were prepared. Zero-order drug release with lag time was achieved by laminating drug-free film onto the reservoir layer, while burst effect was observed on cast-on film. The rate controlling membrane was either attached to or cast directly into the reservoir. The release rate was independent on the reservoir composition but dependent on the composition of rate-controlling membrane. In growth inhibitory test of cephalexin from Eudragit RS film to Streptococcus Mutans, the disk even after release test for 72 hours showed more bacterial growth inhibition than that of control. Permeation of drug through rat skin was proportional to the HPC fraction in the film. We could control the release of cephalexin from the film by changing the fraction of Eudragit RS, HPC and DEP content. Consequently, Eudragit RS/HPC film was found to be very effective system for local delivery of drugs.

• Journal of Pharmaceutical Investigation
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• v.37 no.3
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• pp.193-196
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• 2007

This study aimed to evaluate and develop $Eudragit^{(R)}$-coated pellets based on the dissolution using the paddle method. As coating materials, two types of $Eudragit^{(R)}$ were applied to obtain either sustained release form or fast released form. The dissolution test was carried out in phosphate buffer solution (pH 6.5) at $37^{\circ}C$, 100 rpm. In order to develop a sustained release preparation containing felodipine, a comparative dissolution study was done using commercial product as a control. The dissolution at 30 min of felodipine from $Eudragit^{(R)}$ RS or RL-coated pellets were 0.96% and 99.65, respectively. The weight ratio of $Eudragit^{(R)}$ RL pellets to RS pellets altered the dissolution rate, but did not optimize the dissolution rate. However, the sustained dissolution of felodipine from pellets was optimized by varying the coating ratios of $Eudragit^{(R)}$ RS. It is suggested that the coating ratio of pellets is the main factor which controls dissolution rate. Taken together, $Eudragit^{(R)}$ RS 30D-coated pellets showed the most comparable dissolution rate pattern to commercial product, $Splendil^{(R)}$. This sustained release pellets for oral delivery system of felodipine was simply manufactured, and drug release behavior was highly reproducible.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1992.05a
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• pp.64-64
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• 1992

1. Eudragit RS, RL, E, S 및 L을 이용하여 유중건조법으로 제조한 $\beta$-락탐계 항생제 (Amoxicillin, Cephalexin) 마이크로캅셀 모두가 구상 성형성과 정립성이 양호한 결과를 얻었다. 2. 분리 분산제 (aluminium tristearate)의 양을 고정시켰을 때에는 일정한 입자 분포도를 가지는 마이크로캅셀을 얻을 수 있었고, 양을 증가시켰을 때에는 입자 크기는 작아 졌으며, 용출율은 증가하였다. 3. Eudragit RS 및 S 마이크로캅셀제제로부터의 약물용출은 저조하였고, Eudragit RL 및 L 제제로부터의 약물용출은 양호하였다. 따라서 Eudragit RS/RL 마이크로캅셀제제에서는 Eudragit RL의 양을 증가시킬수록 약물의 용출율이 증가하였으며, Eudragit S/L 마이크로캅셀제제에서는 Eudragit L의 양을 증가시킬수록 약물의 용출율이 증가하였다. 약물방출 실험결과, Amoxicillin 함유Eudragit RS/RL (25/75) 마이크로캅셀, cephalxin함유 Eudragit RS/RL (75/25) 마이크로캅셀 및 Eudragit S/L (75/25) 마이크로캅셀제제는 유용한 제제로 펑가되었다. 또한 수용성 고분자인 polyethylene glycol을 혼합하어 제조하는 것에 의해 방출조절성 마이크로캅셀의 제조가 가능하였다. 유중건조법을 이용하여 본 연구방법으로 저조한 마이크로캅셀제제는 투어횟수를 줄일 수 있을 뿐만 아니라 생체에 대해 안전하고 재현성에 확보되는 유용한 제제로 판단된다. 앞으로 연구를 계속 수행하여, 특히 약물의 물리화학적 성질 및 생제내 투어 후의 생물약제학적 펑가를 엄격히 하므로써 안정성이 심히 문제시되는 다용 약물계열에 대한 조절방출성제제의 개발을 기대할 수 있다.은 해리항수의 역수이므로 해리항수가 적을수록 $\beta$ 수용체에 대한 친화력이 큰 약물이다. 시사되었으며, 이 조직에서 또한 5-$HT_2$와 5-$HT_3$ 수용체의 존재를 확인하고 각각의 기능을 분명히 했다.가 수월하게 하였고 메모리를 동적으로 관리할 수 있게 하였다. 또한 기존의 smpl에 디버깅용 함수 및 설비(facility) 제어용 함수를 추가하여 시뮬레이션 프로그램 작성을 용이하게 하였다. 예를 들면 who_server(), who_queue(), pop_Q(), push_Q(), pop_server(), push_server(), we(), wf(), printfct() 같은 함수들이다. 또한 동시에 발생되는 사건들의 순서를 조종하기 위해, 동시에 발생할 수 있는 각각의 사건에 우선순위를 두어 이 우선 순위에 의하여 사건 리스트(event list)에서 자동적으로 사건들의 순서가 결정되도록 확장하였으며, 설비 제어방식에 있어서도 FIFO, LIFO, 우선 순위 방식등을 선택할 수 있도록 확장하였다. SIMPLE는 자료구조 및 프로그램이 공개되어 있으므로 프로그래머가 원하는 기능을 쉽게 추가할 수 있는 장점도 있다. 아울러 SMPLE에서 새로이 추가된 자료구조와 함수 및 설비제어 방식등을 활용하여 실제 중형급 시스템에 대한 시뮬레이션 구현과 시스템 분석의 예를 보인다._3$", chain segment, with the activation energy of carriers from the shallow trap with 0.4[eV], in he amorphous regions.의 증발산율은 우기의 기상자료를 이용하여 구한 결과 0.05 - 0.10 mm/hr 의 범위로서 이로 인한 강우손실량은 큰 의미가 없음