Dense gas techniques, which utilize the properties of fluids in the vicinity of the critical point, are increasingly being used for the processing of pharmaceuticals. Dense gases are unique solvents that can be used for extractions, chromatographic separations, and chemical syntheses because of their liquidlike solvation power and gaslike mass-transfer properties. The processes can be conducted at moderate temperatures and are thus suitable for many heat-labile compounds such as proteins, biocompatible polymers, and pharmaceuticals. The products formed by densegas processes are generally free of residual solvent. Recent applications of dense gas techniques have focused on micronization; crystallization of high-purity particles; sterilization; and drug formulations, including the formation of liposomes and drug coatings. The following review presents examples of drug extraction, separation, synthesis, sterilization, and particle formation and demonstrates the broad application of dense gases for drug formulation purposes in the pharmaceutical industry.

Using ASES, microparticles of itraconazole were produced with an increased dissolution rate compared with raw material and commercially available product.

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Absorption spectra have been recorded for eight common anaesthetic agents in the ultraviolet range 187-300 nm. Spectra for the agents in aqueous solution showed only minor differences from those obtained in the gaseous state, and the ratios of the absorbances were roughly proportional to the water/gas partition coefficients. The spectra for different agents overlapped each other, and those for methoxyflurane and diethyl ether are entirely overlapped by the absorption curve of oxygen. Cyclopropane showed no absorption in the range tested but, for other agents, ultraviolet analysis is convenient and sensitive. The possibility of interference with analysis for other substances is discussed.