1.
Unga, Johan, 1976, et al.
(författare)
Relating solubility data of parabens in liquid PEG 400 to the behaviour of PEG 4000-parabens solid dispersions
2009
Ingår i: European journal of pharmaceutics and biopharmaceutics. - : Elsevier BV. - 0939-6411 .- 1873-3441. ; 73:2, s. 260-268
Tidskriftsartikel (refereegranskat) abstract
The solid state behaviour of polyethylene glycol 4000 (PEG 4000) and dispersions of a homologous series of parabens (methyl- (MP), ethyl- (EP), propyl- (PP) and butyl- (BP)) were examined and compared to the paraben solubility in liquid PEG 400. Dispersions were prepared by co-melting different amounts of paraben (5-80% (w/w)) and PEG 4000 and were studied using a combination of differential scanning calorimetry (DSC) and small and wide angle X-ray diffraction (SAXD/WAXD). Depending on the concentration of parabens in the dispersions, DSC showed melting peaks from folded and unfolded forms of PEG, a eutectic melting and melting of pure parabens. The fraction of folded PEG increased and the melting temperatures of both PEG forms decreased with increasing paraben content. In an apparent phase diagram of PP-PEG dispersions a eutectic mixture appeared above 5% PP. In addition, a melting peak corresponding to the paraben appeared for dispersion containing more than 60% PP. Similar phase diagrams were shown for the other parabens. The SAXD data and a 1D correlation function analysis revealed that MP and BP were incorporated into the amorphous domains of the lamellae of solid PEG to a higher degree than EP and PP. In addition, the lamellae thickness of PEG and the fraction of amorphous domains increased more for MP and BP compared to EP and PP. BP showed the highest solubility of the parabens followed by MP, EP and PP in both liquid and solid PEG. Furthermore, the thickness of the amorphous domains of the PEG in the different parabens-PEG dispersions could be correlated to the solubility in liquid PEG 400.
2.
Bramer, Tobias, et al.
(författare)
Implications of regular solution theory on the release mechanism of catanionic mixtures from gels
2009
Ingår i: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 71:2, s. 214-225
Tidskriftsartikel (refereegranskat) abstract
The aim of this study was to apply the regular solution theory of mixed micelles to gain new insights on the drug release mechanism, when using catanionic mixtures as a method of obtaining prolonged release from gels. Synergistic effects were investigated at equilibrium and quantified in terms of regular solution theory interaction parameters. The drug release from catanionic aggregates was studied both in a polymer free environment, using dialysis membranes, and in gels, using a modified LISP paddle method. The drug release kinetics was modelled theoretically by combining the regular solution theory with Fick's diffusion laws assuming a contribution to the transport only from monomeric species (stationary aggregates). The theoretical predictions were found to be in reasonably good agreement with experiments. An analysis of the calculated distribution of species between aggregated and monomeric states was shown to provide further insights into the release mechanism.
3.
Frenning, Göran, et al.
(författare)
An effective-medium analysis of confined compression of granular materials
2009
Ingår i: Powder Technology. - : Elsevier BV. - 0032-5910 .- 1873-328X. ; 194:3, s. 228-232
Tidskriftsartikel (refereegranskat) abstract
A simplified model for confined compression of granular materials is considered, which idealizes the collection of particles as a (central) force network. Applying an effective-medium procedure, an equation with micromechanically well-defined parameters is derived, which relates the applied pressure to the engineering strain of the powder during uniaxial compression. Despite the simplicity of the model, comparison with experimental data for mm-sized spherical granules indicates that this equation is able to satisfactorily predict the overall compression profile from single-particle data.
4.
Frenning, Göran, et al.
(författare)
Aspects of pharmaceutical physics
2009. - 5
Ingår i: Modern Pharmaceutics, Volume 2. - New York : Informa Healthcare USA. - 9781420065688
Bokkapitel (övrigt vetenskapligt/konstnärligt)
5.
Frenning, Göran, et al.
(författare)
Effective Kawakita parameters for binary mixtures
2009
Ingår i: Powder Technology. - : Elsevier BV. - 0032-5910 .- 1873-328X. ; 189:2, s. 270-275
Tidskriftsartikel (refereegranskat) abstract
Despite the fact that many industrial processes use mixtures of powders with different physical and mechanical properties, most fundamental studies of powder compression have focused on single-component systems. There is thus an obvious need for an improved understanding of the compression behaviour of mixtures of particulate and granular solids. In this contribution, we show that the Kawakita equation may be particularly useful in this regard. The reason for this is that the degree of compression (i.e., the ratio between the volume reduction and the initial powder volume) for sufficiently high compression pressures P is a linear function of I I P. For ideal mixtures, for which the volume of each component may be determined independently of the others, this linearity implies that effective Kawakita parameters for the mixture may be readily expressed in terms of the parameters of its components. In order to validate the proposed approach, binary mixtures of mm-sized spherical agglomerates prepared by wet granulation followed by extrusion and spheronization were investigated experimentally. Predicted and measured Kawakita parameters were generally in good agreement, indicating that the assumption of ideal mixing behaviour is valid for this type of systems.
