Differential Scanning Calorimetry of Chloramphenicol Palmitate and the Phase-Transitional Behavior of Chloramphenicol Palmitate observed during the Preparation of Its Oral Suspension

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Differential scanning calorimetry was carried out to elucidate the properties of two metastable forms of chloramphenicol palmitate (δ form and sub-α form) and the occurrence and the role of the sub-α form during manufacturing of chloramphenicol palmitate oral suspension. The δ form, a new form, was obtained when the small amount of melted chloramphenicol palmitate was cooled very rapidly to below 0° and it was converted to the sub-α form at 23° on heating. The X-ray diffraction pattern of the δ form was distinguished from that of any other forms reported. The other form, sub-α, was obtained by warming the δ form or directly from the melt by rapid cooling. It was transformed to the α form while liberating heat from about 40° through about 75°. The X-ray diffraction pattern, infrared absorption spectra, the behavior in the hot stage of the polarizing microscope and the differential scanning calorimetric curves suggested that the sub-α form is composed of the crystallites of the α form. Estimated thermodynamic values at the 95% confidence limit were ; ΔH_<melt→sub-α>=-9.2±0.2kcal/mole, ΔH_<melt→δ>=-2.8±0.5 kcal/mole, ΔH_<δ→sub-a>=-2.2±0.7 kcal/mole, and ΔH_<sub-α→α>=-2.0±0.3 (the sub-α form directly form the melt) and -6.1±0.9 kcal/mole (the sub-α form via the δ form). The supercooled dispersion of chloramphenicol palmitate in the emulsifier solution turned into the suspension while stirring. The first solid state of the chloramphenicol palmitate was estimated to be the sub-α form and it was transformed to the α-form gradually.
公益社団法人日本薬学会の論文
1973-09-25

Differential Scanning Calorimetry of Chloramphenicol Palmitate and the Phase-Transitional Behavior of Chloramphenicol Palmitate observed during the Preparation of Its Oral Suspension

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