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  • Thermodynamics of water-solid interactions in crystalline and amorphous pharmaceutical materials.

Thermodynamics of water-solid interactions in crystalline and amorphous pharmaceutical materials.

Journal of pharmaceutical sciences (2013-12-12)
Mark Sacchetti
ABSTRACT

Pharmaceutical materials, crystalline and amorphous, sorb water from the atmosphere, which affects critical factors in the development of drugs, such as the selection of drug substance crystal form, compatibility with excipients, dosage form selection, packaging, and product shelf-life. It is common practice to quantify the amount of water that a material sorbs at a given relative humidity (RH), but the results alone provide minimal to no physicochemical insight into water-solid interactions, without which pharmaceutical scientists cannot develop an understanding of their materials, so as to anticipate and circumvent potential problems. This research was conducted to advance the science of pharmaceutical materials by examining the thermodynamics of solids with sorbed water. The compounds studied include nonhygroscopic drugs, a channel hydrate drug, a stoichiometric hydrate excipient, and an amorphous excipient. The water sorption isotherms were measured over a range of temperature to extract the partial molar enthalpy and entropy of sorbed water as well as the same quantities for some of the solids. It was found that water-solid interactions spanned a range of energy and entropy as a function of RH, which was unique to the solid, and which could be valuable in identifying batch-to-batch differences and effects of processing in material performance.

MATERIALS
Product Number
Brand
Product Description

Supelco
Genistein, analytical standard
Supelco
Erythromycin A hydrate, VETRANAL®, analytical standard
Sigma-Aldrich
Indomethacin, meets USP testing specifications
Sigma-Aldrich
Genistein, synthetic, ≥98% (HPLC), powder
Sigma-Aldrich
Genistein, from Glycine max (soybean), ~98% (HPLC)
Sigma-Aldrich
Indomethacin, 98.5-100.5% (in accordance with EP)
Sigma-Aldrich
Griseofulvin, from Penicillium griseofulvum, 97.0-102.0%
Indomethacin, European Pharmacopoeia (EP) Reference Standard
Supelco
Indomethacin, Pharmaceutical Secondary Standard; Certified Reference Material
USP
Griseofulvin, United States Pharmacopeia (USP) Reference Standard
USP
Indomethacin, United States Pharmacopeia (USP) Reference Standard
Supelco
Griseofulvin, Pharmaceutical Secondary Standard; Certified Reference Material
USP
Griseofulvin Permeability Diameter, United States Pharmacopeia (USP) Reference Standard