Preparation and in vitro degradation properties of polylactide microcapsules.

Makino, Kimiko; Arakawa, Masayuki; Kondo, Tamotsu

doi:10.1248/cpb.33.1195

Cited by 181 publications

(85 citation statements)

References 9 publications

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“…This result may be explained using the theory of general acid-base catalysis, where cleavage of the ester bonds in the polymer is induced by an excess of H + or OH-ions in the media, with faster hydrolysis obtained under alkaline conditions. This was reported by Makino et al 9 who observed a significantly faster decrease of weight-average MW of poly(D,L-PLA) microcapsules in highly alkaline media (pH 9.6) than in highly acidic (pH 1.6) or nearly neutral conditions (pH 7.4).…”

Section: E558supporting

confidence: 68%

“…This was highlighted in the guidelines, which resulted from an American Association of Pharmaceutical Scientists/International Pharmaceutical Federation (AAPS/FIP) sponsored conference on dissolution/in vitro release testing of novel/special dosage forms. 7 Recognizing that drug release is governed by the slowly degrading polymer, research in the past decade has focused on accelerating polymer degradation using elevated temperatures, 8 buffer type, and pH [9][10][11][12][13] and comparing the results to physiologically degraded material. Buchholz 8 examined the effect of 2 temperatures, 37-C and 80-C, on the in vitro degradation of D,L -PLA.…”

Section: Introductionmentioning

confidence: 99%

“…In another study by Bergsma et al, 10 degradation behavior of L -and D,L -PLA was studied at 90-C. Degradation at temperatures between 25-C and 50-C of polyglycolic acid (PGA) sutures 11 and 50:50 PLGA devices 12 has also been reported. Makino et al 9 reported the degradation of L -and D,L -PLA microcapsules at varying temperatures, ionic strength, and pH of medium. All these studies showed that polymer degradation rate was accelerated at elevated temperatures, thereby reducing the time required for in vitro experiments.…”

Section: Introductionmentioning

confidence: 99%

“…However, changes in the type of buffer or pH (acidic or alkaline) have been reported to accelerate polymer degradation, owing to the difference in the mechanism of PLA and PLGA ester hydrolysis. 9 An application of these findings was demonstrated by Shameem et al 14 who investigated peptide release from PLGA microspheres by using elevated temperature, buffer, and surfactant to accelerate release kinetics and reduce the time required for in vitro release studies. Release was assessed using the "sample and separate" method with residual peptide analysis from the microspheres at predetermined time points.…”

Section: Introductionmentioning

confidence: 99%

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A model-dependent approach to correlate accelerated with real-time release from biodegradable microspheres

2005

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The purpose of this study was to determine the feasibility of applying accelerated in vitro release testing to correlate or predict long-term in vitro release of leuprolide poly(lactideco-glycolide) microspheres. Peptide release was studied using a dialysis technique at 37°C and at elevated temperatures (50°C-60°C) in 0.1M phosphate buffered saline (PBS) pH 7.4 and 0.1M acetate buffer pH 4.0. The data were analyzed using a modification of the Weibull equation. Peptide release was temperature dependent and complete within 30 days at 37°C and 3 to 5 days at the elevated temperatures. In vitro release profiles at the elevated temperatures correlated well with release at 37°C. The shapes of the release profiles at all temperatures were similar. Using the modified Weibull equation, an increase in temperature was characterized by an increase in the model parameter, α, a scaling factor for the apparent rate constant. Complete release at 37°C was shortened from 30 days to 5 days at 50°C, 3.5 days at 55°C, 2.25 days at 60°C in PBS pH 7.4, and 3 days at 50°C in acetate buffer pH 4.0. Values for the model parameter β indicated that the shape of the release profiles at 55°C in PBS pH 7.4 (2.740) and 50°C in 0.1M acetate buffer pH 4.0 (2.711) were similar to that at 37°C (2.677). The E a for hydration and erosion were determined to be 42.3 and 19.4 kcal/mol, respectively. Polymer degradation was also temperature dependent and had an E a of 31.6 kcal/mol. Short-term in vitro release studies offer the possibility of correlation with long-term release, thereby reducing the time and expense associated with longterm studies. Accelerated release methodology could be useful in the prediction of long-term release from extended release microsphere dosage forms and may serve as a quality control tool for the release of clinical or commercial batches.

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Section: E558supporting

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A model-dependent approach to correlate accelerated with real-time release from biodegradable microspheres

2005

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“…Further insight can be gained by an investigation of the drug's stability under elevated temperatures. Verification of the validity of using these conditions could include an Arrhenius plot after obtaining release rate profiles from linearized release profiles [85]. The question remains, however, what constitutes a significant change in the dissolution profile, since defined limits for the consideration of percent drug remaining in the medium after a designated test time are not available thus far in any guidance [86].…”

Section: Accelerated In Vitro Release Testingmentioning

confidence: 99%

Profiling in vitro drug release from subcutaneous implants: a review of current status and potential implications on drug product development

Iyer¹,

Barr²,

Karnes³

2006

Biopharm & Drug Disp

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This review presents current methods and strategies for studying the release characteristics of drugs from subcutaneous implant dosage forms. Implants are dosage forms that are subcutaneously placed with the aid of surgery or a hypodermic needle, and are designed to release drugs over a prolonged period of time. In most cases, the objective of a release test is to identify sufficiently discriminatory procedures that in turn would provide data to set meaningful specifications. Additional information obtained from successful in vitro-in vivo correlations (IVIVC) and accelerated drug release tests are extremely useful during drug product development.Although several workers have employed different methods to monitor drug release from these dosage forms, the use of the compendial Apparatus 4 (flow-through) device has been recommended in a publication on FIP/AAPS Guidelines for drug release testing of modified release dosage forms. However, most of method development with this device has focused on oral immediate or controlled release dosage forms and little published information is available on implants. Two recent reports on workshops provide useful information on methods to evaluate drug release from controlled-release parenterals such as implants, including IVIVC and accelerated release testing. Details on such studies, however, are generally not found in the literature; possibly because of the high proprietary value of methodologies for establishing release specifications of implant dosage forms. This article reviews the current status of methodologies used in the investigation of drug release from subcutaneous implants with an emphasis on mechanistic, product development and regulatory perspectives.

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Hydrolytic degradation characteristics of aliphatic polyesters derived from lactic and glycolic acids

Li¹

1999

J. Biomed. Mater. Res.

598

417

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During the past decade, important advances have been made in the understanding of the hydrolytic degradation characteristics of aliphatic polyesters derived from lactic acid (LA) and glycolic acid (GA). Degradation of large poly(LAGA) (PLAGA) polymers is autocatalyzed by carboxyl end groups initially present or generated upon ester bond cleavage. Faster internal degradation and degradation-induced morphological and compositional changes are three of the most important findings deduced from the behaviors of various PLAGA polymers. This review presents the state of the art in this domain. The research efforts are focused on detailing the degradation mechanism and the effects of various factors on the degradation of PLAGA polymers. An attempt is also made to elaborate a scheme that can be used to predict degradation characteristics of these polymers from their initial composition and morphology.

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Preparation and in vitro degradation properties of polylactide microcapsules.

Cited by 181 publications

References 9 publications

A model-dependent approach to correlate accelerated with real-time release from biodegradable microspheres

A model-dependent approach to correlate accelerated with real-time release from biodegradable microspheres

Profiling in vitro drug release from subcutaneous implants: a review of current status and potential implications on drug product development

Hydrolytic degradation characteristics of aliphatic polyesters derived from lactic and glycolic acids

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