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Hüttenrauch, R; Fricke, S.; Zielke, Petra

doi:10.1023/a:1016397719020

Cited by 125 publications

(14 citation statements)

References 12 publications

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“…Using X-ray and infrared measurements, previous authors (Davison 1955;Miyazawa et a1 1961Miyazawa et a1 ,1962Price & Kilb 1962) noted a tendency for polyethylene glycols of molecular weight 4000 and higher to form crumpled helix structures in the solid state. Huttenrauch & Fricke (1981b) suggested that the polymer molecules also exist in the anhydrous PEG 400 liquid as the linear or, so-called, 'zig-zag' form. The addition of small quantities (<5%) of water was considered to induce helix formation in the system, thereby increasing the viscosity.…”

Section: Discussionmentioning

confidence: 99%

The solubility of 17 β-oestradiol in aqueous polyethylene glycol 400

Groves¹,

Bassett²,

Sheth³

1984

Journal of Pharmacy and Pharmacology

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The solubility of 17 beta-oestradiol (E2) in aqueous solutions of polyethylene glycol (PEG) 400 has been measured at 35 degrees C. Up to 80% w/w PEG the solubility data conform to a log linear equation ln S = ln Sw + f sigma where S is the E2 concentration in the water/cosolvent mixture, Sw is E2 solubility in water, f is the weight fraction of PEG 400 and sigma is a parameter representing the solubilizing power of the cosolvent for the drug. Above 80% PEG the relationship becomes less convincing, with significant deviation from anticipated values. Reasons for these aberrations are discussed. It is suggested that conformational changes may be induced in the PEG by the addition of small quantities of water. Deviations noted for the melting point, viscosity and density data of PEG 400-water solutions may also confirm this suggestion.

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Section: Discussionmentioning

confidence: 99%

The solubility of 17 β-oestradiol in aqueous polyethylene glycol 400

Groves¹,

Bassett²,

Sheth³

1984

Journal of Pharmacy and Pharmacology

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“…This causes disordering or amorphisation of the initially crystalline particle surface [25,26]. Mixing with the coarse carrier results in a faster increase in apparent solubility than does mixing with the fine carrier.…”

Section: Resultsmentioning

confidence: 99%

Mixing Time Effects on the Dispersion Performance of Adhesive Mixtures for Inhalation

et al. 2013

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This paper deals with the effects of mixing time on the homogeneity and dispersion performance of adhesive mixtures for inhalation. Interactions between these effects and the carrier size fraction, the type of drug and the inhalation flow rate were studied. Furthermore, it was examined whether or not changes in the dispersion performance as a result of prolonged mixing can be explained with a balance of three processes that occur during mixing, knowing drug redistribution over the lactose carrier; (de-) agglomeration of the drug (and fine lactose) particles; and compression of the drug particles onto the carrier surface. For this purpose, mixtures containing salmeterol xinafoate or fluticasone propionate were mixed for different periods of time with a fine or coarse crystalline lactose carrier in a Turbula mixer. Drug detachment experiments were performed using a classifier based inhaler at different flow rates. Scanning electron microscopy and laser diffraction techniques were used to measure drug distribution and agglomeration, whereas changes in the apparent solubility were measured as a means to monitor the degree of mechanical stress imparted on the drug particles. No clear trend between mixing time and content uniformity was observed. Quantitative and qualitative interactions between the effect of mixing time on drug detachment and the type of drug, the carrier size fraction and the flow rate were measured, which could be explained with the three processes mentioned. Generally, prolonged mixing caused drug detachment to decrease, with the strongest decline occurring in the first 120 minutes of mixing. For the most cohesive drug (salmeterol) and the coarse carrier, agglomerate formation seemed to dominate the overall effect of mixing time at a low inhalation flow rate, causing drug detachment to increase with prolonged mixing. The optimal mixing time will thus depend on the formulation purpose and the choice for other, interacting variables.

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“… 27 , 37 Moreover, even if milling is one of the most effective ways to lower the activation barrier for different types of chemical reactions (tribochemistry), 38 many substances undergo decomposition during this process. 39 To avoid this undesired effect, very often, the temperature of the milling is lowered (cryomilling/cryogrinding). 40 However, it should be pointed out that there is a reported case of the API—furosemide—which undergoes chemical decomposition during cryogenic grinding alone as well as in the system with inulin or poly(vinylpyrrolidone) (PVP) polymer.…”

Section: Introductionmentioning

confidence: 99%

Studies on the Vitrified and Cryomilled Bosentan

et al. 2021

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In this paper, several experimental techniques [X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetry, Fourier transform infrared spectroscopy, and broad-band dielectric spectroscopy] have been applied to characterize the structural and thermal properties, H-bonding pattern, and molecular dynamics of amorphous bosentan (BOS) obtained by vitrification and cryomilling of the monohydrate crystalline form of this drug. Samples prepared by these two methods were found to be similar with regard to their internal structure, H-bonding scheme, and structural (α) dynamics in the supercooled liquid state. However, based on the analysis of α-relaxation times (dielectric measurements) predicted for temperatures below the glass-transition temperature ( T g ), as well as DSC thermograms, it was concluded that the cryoground sample is more aged (and probably more physically stable) compared to the vitrified one. Interestingly, such differences in physical properties turned out to be reflected in the lower intrinsic dissolution rate of BOS obtained by cryomilling (in the first 15 min of dissolution test) in comparison to the vitrified drug. Furthermore, we showed that cryogrinding of the crystalline BOS monohydrate leads to the formation of a nearly anhydrous amorphous sample. This finding, different from that reported by Megarry et al. [ 21492830 Carbohydr. Res. 2011 346 1061 1064 ] for trehalose (TRE), was revealed on the basis of infrared and thermal measurements. Finally, two various hypotheses explaining water removal upon cryomilling have been discussed in the manuscript.

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Cited by 125 publications

References 12 publications

The solubility of 17 β-oestradiol in aqueous polyethylene glycol 400

The solubility of 17 β-oestradiol in aqueous polyethylene glycol 400

Mixing Time Effects on the Dispersion Performance of Adhesive Mixtures for Inhalation

Studies on the Vitrified and Cryomilled Bosentan

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