ビタミンD_2散剤の安定性に関する研究(第2報) : 賦形剤の表面酸性とビタミンD_2の異性化の関係その2

概要

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Stability of vitamin D_2 (D_2) in powder preparations mixed with various excipients was examined in the presence or absence of air. In a preparation with CaHPO_4 (acid strength of surface pK_a 0.8 to 1.5), containing 5% D_2 and 1% butylated hydroxyanisole (BHA), the D_2 loss was 72% in vacuum (1 mmHg) and 78% in air under low humidity after a 5 days storage at 37°. With lactose (pK_a 4.0 to 4.8), the D_2 loss was very small under the same conditions. These results show that the degradation of D_2 mixed with CaHPO_4 proceeds through isomerization rather than by oxidation. Such phenomenon is generally observed with excipients such as synthetic aluminum silicate, magnesium trisilicate, talc or CaSO_4,having a pK_a of 3.3. When the preparations were stored under high humidity, the stability of D_2 increased markedly because the surface acidity of the excipients decreased through adsorption of moisture during storage. As isomerization products of D_2,a new isomer was found together with isocalciferol and isotachystreol.
社団法人日本薬学会の論文
1969-07-25