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Gao, Ping; Nixon, Phillip R.; Skoug, John W.

doi:10.1023/a:1016246028338

Cited by 61 publications

(15 citation statements)

References 6 publications

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“…[1][2][3][4] This conclusion is supported by our recent study of the concentration dependence of drug diffusivity in the presence of the major components (drug, lactose, and water) in HPMC gel solution. 3 Using the Higuchi equation for soluble drugs, we demonstrated that the dependence of drug diffusivity upon the concentrations of HPMC, lactose, and drug can be correlated to the change in drug release rate as a function of formulation composition.…”

Section: Introductionsupporting

confidence: 61%

“…This conclusion is consistent with our studies of drug diffusivity in HPMC gels. 3,4 We caution, however, that our conclusions are strictly valid for soluble drugs at moderate to low matrix loadings. For insoluble drugs or soluble drugs at very high loadings, 31 matrix dissolution determines drug release rate.…”

Section: Resultsmentioning

confidence: 76%

“…3 Using the Higuchi equation for soluble drugs, we demonstrated that the dependence of drug diffusivity upon the concentrations of HPMC, lactose, and drug can be correlated to the change in drug release rate as a function of formulation composition. 4 However, a limitation of this modeling work is the lack of consideration of swelling kinetics of the matrix (the Higuchi model assumes a nonswelling, nondissolving matrix 5 ).…”

Section: Introductionmentioning

confidence: 99%

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Swelling of Hydroxypropyl Methylcellulose Matrix Tablets. 2. Mechanistic Study of the Influence of Formulation Variables on Matrix Performance and Drug Release

Gao

Skoug

Nixon

et al. 1996

Journal of Pharmaceutical Sciences

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158

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We characterized the effect of hydroxypropyl methylcellulose (HPMC)/lactose ratio and HPMC viscosity grade (molecular weight) on solute release and swelling of matrix tablets. We used a semiquantitative optical imaging method to monitor the swelling of matrices with HPMC content from 20% to 80% (w/w) and four viscosity grades. Several aspects of the swelling process common to all formulations were revealed: (i) swelling is anisotropic with a preferential expansion in the axial direction, (ii) swelling is isotropic with respect to the gel layer thickness and composition in both axial and radial directions, (iii) the gel layer develops in three stages, and (iv) water penetration is Fickian in nature and essentially constant for all formulations. We monitored simultaneously drug, lactose, and HPMC release. Lactose and drug release rates were superimposed, indicating a similar diffusional release mechanism and no interaction with HPMC. The strong dependence of HPMC release on viscosity grade is explained on the basis of the concept of polymer disentanglement concentration. We analyzed drug release rates using a model for a reservoir-type release system that incorporates swelling kinetics. HPMC/lactose ratio modulates drug release rate by altering drug diffusivity, a function of gel composition. In contrast, HPMC viscosity grade impacts matrix dissolution and gel layer thickness development below a critical molecular weight. For slowly dissolving matrices containing high viscosity grade (> 4000 cps) HPMC, similar drug release rates are observed mainly due to the same drug diffusivity as a result of the identical gel composition and thickness. For fast dissolving matrices (< or = 100 cps) swelling inhomogeneity is proposed as being responsible for a higher apparent drug diffusivity and release rate.

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Section: Introductionsupporting

confidence: 61%

Section: Resultsmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Swelling of Hydroxypropyl Methylcellulose Matrix Tablets. 2. Mechanistic Study of the Influence of Formulation Variables on Matrix Performance and Drug Release

Gao

Skoug

Nixon

et al. 1996

Journal of Pharmaceutical Sciences

Self Cite

158

View full text Add to dashboard Cite

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“…In this case, the swelling behavior of MCC allowed further penetration of the aqueous medium, resulting in rapid erosion of the polymer matrices. In addition, lactose in aqueous solution plays a role as important physical barrier, affecting the release kinetics, by reducing the tortuosity of the diffusion pattern of the drug [14]. However, if it were mixed with Methocel K15 MCR, the polymer concentration would lead the release rate of the drug.…”

Section: Effect Of Lactosementioning

confidence: 99%

In-vitro Studies of Pentoxifylline Controlled-Release from Hydrophilic Matrices

Rahman¹,

Islam²,

Wahed³

et al. 2009

J. Sci. Res.

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Methocel K15 MCR (a modified hydroxypropylmethylcellulose) matrix tablets of pentoxifylline using microcrystalline cellulose (MCC), starch and lactose were prepared by wet granulation process. There was no significant difference in drug release between the hydrophilic matrices when the Methocel K15 MCR concentration was modified in low percentage. The release of pentoxifylline was influenced by the presence of microcrystalline cellulose, and by the different concentrations of starch and lactose. The data obtained proved that the formulation with 12.5% Methocel K15 MCR and 20% lactose is more useful for a controlled release pentoxifylline, due to the percentage released after 8 hours is nearly to 65%. There was no significant change on release profile after three months storage of tablets. The best-fit release kinetics was achieved with the Higuchi model, followed by the first-order plot.

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“…This review also includes a discussion on Na CMC for the slow release of cardiovascular drugs. The use of HPMC as a SR system has been well documented [7][8][9][10][11][12][13][14][15][16][17][18]. Hogan [19] reviewed the use of HPMC in pharmaceuticals.…”

Section: Introductionmentioning

confidence: 99%