Chloramphenicol-urea eutectic

These are prepared by rapid solidification of the fused melt of two components that show complete liquid miscibility but negligible solid-solid solubility. Thermodynamically, such a system is an intimately blended physical mixture of its two crystalline components. Thus, the X-ray diffraction pattern of a eutectic constitutes an additive composite of the two components. A phase diagram of a two-component system is shown in Fig. 1. Examples of this type include phenacetin-phenobarbital, chloramphenicol-urea, griseofulvin-sucdnic acid, paracetamol-urea, and the dispersions of giiseofulvin and tolbutamide in polyethylene glycol-(PEG-2000).[ ... 

Other systems that form eutectic mixmres are chloramphenicol-urea, sulfathiazole-urea, and niacinamide-ascorbic acid. The solid solution of chloramphenicol in urea was found to dissolve twice as rapidly as a physical mixmre of the same composition and about four times as rapidly as the pure dmg. In vivo, however, the system failed to display improved bioavailability. On the other hand, the eutectic mixmre of sulfathiazole-urea did give higher blood levels than pure sulfonamide. 

Sekigicjo K, Obi N, Ueda Y. Studies on absorption of eutectic mixtures. II. Absorption of fused conglomerates of chloramphenicol and urea in rabbits. Chem Pharm Bull 1964 12 134-144. 

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