Freeze-Drying of Drug-Additive Binary Systems. II. : Relationship between Decarboxylation Behavior and Molecular States of p-Aminosalicylic Acid

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The effects of additives on the crystallinity and the stability of freeze-dried p-aminosalicylic acid (PAS) have been investigated. Aqueous PAS solutions, to which various amounts of pullulan were added, were freeze-dried. The degradation rates of PAS at 80℃ increased with increasing amount of pullulan added and were also affected by the freezing conditions. It was suggested from the powder X-ray diffractograms that the stability of PAS was closely related to the content of amorphous fractino of PAS in the freeze-dried samples. In the freeze-dried samples containing α-cyclodextrin (α-CD) as the additive, the fastest degradation rate of PAS was observed at the mixing molar ratio (α-CD/PAS) of 0.5 (rapid freezing condition) or 1.0 (slow freezing condition). These results coulde be explained in terms of the three possible states of PAS in the freeze-dried sample with α-CD : (A) the crystalline state, almost stable; (B) the included state in the α-CD cavity, moderately unstable; (C) the dispersed state in the intermolecular hydrogen-bonding network of α-CDs, unstable.
公益社団法人日本薬学会の論文
1989-11-25