Thermal Characterization of Citric Acid Solid Dispersions with Benzoic Acid and Phenobarbital

Timko, Robert J.; Lordi, Nicholas G.

doi:10.1002/jps.2600680523

Cited by 41 publications

(28 citation statements)

References 15 publications

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“…Simmer and Enever [35] reported T g = − 23 °C for citric acid monohydrate, but this result was in conflict with the Timko and Lordi [36] findings for anhydrous citric acid. The glass transition for bulk-prepared citric acid glass was T g = 13.2 °C and for the in situ conditions T g = 10.2 °C.…”

mentioning

confidence: 43%

“…Citric acid as well other organic acids received much attention because they are able to absorb water and alter the radiation balance and finally the climate. It is worthwhile also to note that citric acid solutions, as was observed by Corley and Killoy [57], are stable with regards - [35][36][37][38][39]42]; - [43]; - [45]; - [46]; continuous line is calculated using Eq. (2.2) to time, light and air exposure.…”

mentioning

confidence: 98%

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Properties of Citric Acid and Its Solutions

Apelblat

2014

Citric Acid

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confidence: 43%

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confidence: 98%

Properties of Citric Acid and Its Solutions

Apelblat

2014

Citric Acid

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“…that were placed on hot plates and then cooling the melts in an ice bath, a dry ice-acetone mixture, etc. [2][3][4][5][7][8][9][10][11][12][13][14] Because there could be condensation of moisture over solid dispersions during cooling to low temperatures, strict protection from moisture was necessary in all cases. The scale up challenges may be illustrated with the example of the preparation of a phenytoin-PEG 4000 solid dispersion by Yakou et al 39 The drug-carrier mixture was heated at 250°C under constant stirring until a clear homogeneous melt was obtained, and the melt was air-cooled by spreading on stainless steel trays.…”

Section: Reproducibility Of Physicochemical Propertiessmentioning

confidence: 99%

Solid dispersion of poorly water‐soluble drugs: Early promises, subsequent problems, and recent breakthroughs

Serajuddin

1999

Journal of Pharmaceutical Sciences

1,431

780

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Although there was a great interest in solid dispersion systems during the past four decades to increase dissolution rate and bioavailability of poorly water-soluble drugs, their commercial use has been very limited, primarily because of manufacturing difficulties and stability problems. Solid dispersions of drugs were generally produced by melt or solvent evaporation methods. The materials, which were usually semisolid and waxy in nature, were hardened by cooling to very low temperatures. They were then pulverized, sieved, mixed with relatively large amounts of excipients, and encapsulated into hard gelatin capsules or compressed into tablets. These operations were difficult to scale up for the manufacture of dosage forms. The situation has, however, been changing in recent years because of the availability of surface-active and self-emulsifying carriers and the development of technologies to encapsulate solid dispersions directly into hard gelatin capsules as melts. Solid plugs are formed inside the capsules when the melts are cooled to room temperature. Because of surface activity of carriers used, complete dissolution of drug from such solid dispersions can be obtained without the need for pulverization, sieving, mixing with excipients, etc. Equipment is available for large-scale manufacturing of such capsules. Some practical limitations of dosage form development might be the inadequate solubility of drugs in carriers and the instability of drugs and carriers at elevated temperatures necessary to manufacture capsules.

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“…∆H* R (8) above T g at a constant rate of 30 K/min and then heating through the T g at rates ranging from 5 to 40 K/min. The lines represent least-squares linear fitting.…”

Section: Glass Transition Temperatures Of Dry and Hydratedmentioning

confidence: 99%

Properties of Citric Acid at the Glass Transition

Lü

Zografi

1997

Journal of Pharmaceutical Sciences

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To better understand the properties of citric acid when used in solid dosage forms as an acid-base buffer, we initiated a study of its properties in the amorphous state. Such a state often arises during processes such as lyophilization and wet granulation. In view of inconsistencies in the literature concerning the glass transition temperature, Tg, of citric acid in the dry and hydrated states, we measured the Tg of samples formed by a melt-quench cool sequence in a DSC. We also used DSC to measure Tg', the glass transition temperature of the maximally freeze-concentrated solution. It was shown that dry citric acid has a Tg of 11 degrees C, while that containing 8.6% water (equimolar) has a value of -25 degrees C. The Tg' of a frozen solution of citric acid is -53 degrees C. Measuring Tg for the dry and hydrated samples at various scanning rates allowed measurement of the activation energy for enthalpy relaxation at Tg and enabled estimation of the degree of fragility (or the strength parameter) for both samples. It was shown that citric acid is a fairly fragile liquid expected to exhibit non-Arrhenius dynamic behavior and that the presence of residual water at a level of 8.6% causes a decrease in fragility.

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Thermal Characterization of Citric Acid Solid Dispersions with Benzoic Acid and Phenobarbital

Cited by 41 publications

References 15 publications

Properties of Citric Acid and Its Solutions

Properties of Citric Acid and Its Solutions

Solid dispersion of poorly water‐soluble drugs: Early promises, subsequent problems, and recent breakthroughs

Properties of Citric Acid at the Glass Transition

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