On the use of the Weibull function for the discernment of drug release mechanisms

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A c c e p t e d M a n u s c r i p t Page 4 of 25 A c c e p t e d M a n u s c r i p tsphericity. In such a case, BSA played a role as a surface active agent, replacing PVA. For longer stirring times, BSA was unable to act as an emulsifier.These microparticles showed an uncommon release profile, consisting of a two-step release mechanism, at the pH range studied. Considering that a two-step release mechanism is occurring, the experimental data were adjusted by applying modified power law and Weibull equations in order to describe release mechanism n and release rate constant k, respectively. Each one of the release stages was related to a specific value of n and k. The second stage was driven by a super case II transport mechanism, as a result of diffusion, macromolecular relaxation, and erosion. A third model, described by Hixson-Crowell, confirmed the erosion mechanism.Vit-B 12 diffusion kinetics in aqueous solutions (i.e., without the microparticles) follows a one-step process, being k dependent on the pH, confirming that the two-step release mechanism is a characteristic profile of the developed microparticles. The microparticles released only 2.70% of their initial drug load at pH 2, and 58.53% at pH 10.

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“…The equation 2 gives an insight into the diffusional mechanism, since k' is closely related to the rate constant of release [28].…”

Section: Insert Tablementioning

confidence: 99%

Drug release mechanisms of chemically cross-linked albumin microparticles: Effect of the matrix erosion

Sitta

Guilherme

Silva

et al. 2014

Colloids and Surfaces B: Biointerfaces

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“…For values of ß higher than 1, the drug transport follows a complex release mechanism (Papadopoulou et al, 2006). For Gem-SNEDDS in coated capsules ß value is 2.05 and 3.45 for conventional tablets, neither significant differences were observed between values 720 (p= 0.1099).…”

mentioning

confidence: 91%

“…These ß values has been described as a sigmoid curve indicative of complex release mechanism, the rate of release does not change monotonically. In fact, the release rate initially increases nonlinearly up to the inflection point and thereafter decreases asymptotically (Papadopoulou et al, 2006). Only for t d values which were 6.44 for Gem-SNEDDS in coated capsules and 26.5 for 725 conventional tablets, significant differences were observed (p=0.0001), t d represents the time interval necessary to dissolve or release 63.2% of the drug present in the pharmaceutical dosage form, meaning that in 45 min study, 63.2 % of Gem was released in 6.44 min from SNEDDS, and conventional tablets took 26.5 min.…”

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confidence: 99%

Design and optimization of self-nanoemulsifying drug delivery systems (SNEDDS) for enhanced dissolution of gemfibrozil

Villar

Naveros

Campmany

et al. 2012

International Journal of Pharmaceutics

140

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Self nanoemulsifying drug delivery systems of gemfibrozil were developed under Quality by Design approach for improvement of dissolution and oral absorption. Preliminary screening was performed to select proper components combination. Box-Behnken experimental design was employed as statistical tool to optimize the formulation variables, X1 (Cremophor® EL), X2 (Capmul® MCM -C8), and X3 (lemon essential oil). Systems were assessed for visual characteristics (emulsification efficacy), turbidity, droplet size, polydispersity index and drug release. Different pH media were also assayed for optimization. Following optimization, the values of formulation components (X1, X2, and X3) were 32. 43%, 29.73% and 21.62 %, respectively (16.22% of gemfibrozil). Transmission electron microscopy demonstrated spherical droplet morphology. SNEEDS release study was compared to commercial tablets. Optimized SNEDDS formulation of gemfibrozil showed a significant increase in dissolution rate compared to conventional tablets. Both formulations followed Weibull mathematical model release with a significant difference in td parameter in favour of the SNEDDS. Equally amodelistic parameters were calculated being the dissolution efficiency significantly higher for SNEDDS, confirming that the developed SNEDDS formulation was superior to commercial formulation with respect to in vitro dissolution profile. This paper provides an overview of the SNEDDS of the gemfibrozil as a promising alternative to improve oral absorption. She is an expert in nanotechnology (colloids and nanoparticles) with a wide experience. She has extensive curriculum of published paper about this subject Jose Luis Arias Mediano Ph. D. Professor reseracher, Pharmacy and Pharmaceutical Technology , University of Granada jlarias@ugr.es He is an expert in nanotechnology (colloids and nanoparticles) with a wide experience in this type of investigation. Also is reviewer in specialized pharmaceutical journal. He is an expert in nanotechnology (colloids and nanoparticles) with a wide experience in this type of investigation. Also is reviewer of Pharmaceutical science journals. IJP AUTHOR CHECKLISTDear Author, It frequently happens that on receipt of an article for publication, we find that certain elements of the manuscript, or related information, is missing. This is regrettable of course since it means there will be a delay in processing the article while we obtain the missing details.In order to avoid such delays in the publication of your article, if accepted, could you please run through the list of items below and make sure you have completed the items. Overall Manuscript Electronic artwork format? ---------------------------------------------------TIFF

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“…In fact, the release rate initially increases nonlinearly up to the inflection point and thereafter decreases asymptotically [21].…”

Section: Application Of the Methodsmentioning

confidence: 98%

“…On the use of the Weibull function for the discernment of drug release mechanisms, estimates for ß ⩽ 0.75 indicate Fickian diffusion in either fractal or Euclidian spaces while a combined mechanism (Fickian diffusion and swelling controlled release) is associated with ß values in the range 0.75 < ß < 1. For values of ß higher than 1, the drug transport follows a complex release mechanism [21]. For Gem-SNEDDS in coated capsules ß value is 1.74.…”

Section: Application Of the Methodsmentioning

confidence: 99%

Validated spectrofluorometric method for determination of gemfibrozil in self nanoemulsifying drug delivery systems (SNEDDS)

Villar

Calpena

Bellowa

et al. 2013

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

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HIGHLIGHTSA spectrofluorometric method has been developed for the determination of gemfibrozil.The method is based on the excitation and emission capacities of gemfibrozil.This method allows de determination of the drug in SNEDDS.Results showed linear relationships, low limits of LOD and LOQ with good robustness. GRAPHICAL ABSTRACTValidated spectofluorometric method for determination of gemfibrozil in self nanoemulsifying drug delivery systems (SNEDDS) Article history: ABSTRACT A spectrofluorometric method has been developed and validated for the determination of gemfibrozil. The method is based on the excitation and emission capacities of gemfibrozil with excitation and emission wavelengths of 276 and 304 nm respectively. This method allows de determination of the drug in a selfnanoemulsifying drug delivery system (SNEDDS) for improve its intestinal absorption. Results obtained showed linear relationships with good correlation coefficients (r 2 > 0.999) and low limits of detection and quantification (LOD of 0.075 μg mL −1 and LOQ of 0.226 μg mL −1 ) in the range of 0.2-5 μg mL −1 , equally this method showed a good robustness and stability. Thus the amounts of gemfibrozil released from SNEDDS contained in gastro resistant hard gelatine capsules were analysed, and release studies could be performed satisfactorily.

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On the use of the Weibull function for the discernment of drug release mechanisms

Cited by 653 publications

References 36 publications

Drug release mechanisms of chemically cross-linked albumin microparticles: Effect of the matrix erosion

Drug release mechanisms of chemically cross-linked albumin microparticles: Effect of the matrix erosion

Design and optimization of self-nanoemulsifying drug delivery systems (SNEDDS) for enhanced dissolution of gemfibrozil

Validated spectrofluorometric method for determination of gemfibrozil in self nanoemulsifying drug delivery systems (SNEDDS)

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