Effects of Water-Soluble Polymers on the Crystalline Conversion of Prednisolone in Oil-in-Water Type Ointment Bases

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The effects of methylcellulose (MC) and hydroxypropylcellulose (HPC) on oil-in-water (o/w) type ointment bases and the crystalline conversion from the anhydrous form of prednisolone (A-PD) to its hydrated form (C-PD) in such o/w type ointment bases were studied. The weight loss of the base, that is the volume of water released from the base, was measured in dry conditions and at a low temperature (5℃). The weight loss of the base without MC or HPC (No.1 base) was about 7% in 10d. On the other hand, the weight losses of the base containing MC (No.3 base), and that containing HPC (No.6 base) were about 1% and 4% under the same conditions, respectively. The yield value of each of the bases Nos.1,3,and 6 was measured with a spreading meter. The yield value of No.1 base was smaller than that of the other bases for 24h after preparation at room temperature (25℃). The yield value of No.3 base became lower and that of No.6 base became slightly greater than that of 24 h for 7 d after preparation upon storage at room temperature and humidity (25℃). However, the yield value of No.1 base increased after 7 d. The crystalline conversion of A-PD in o/w type ointment base was measured by the use of an X-ray diffractometer. A-PD was entirely converted into C-PD in No.1 base in only 1 d at 5℃. On the other hand, when MC or HPC was incorporated in the base, the conversion of A-PD to C-PD was retarded. The periods required for complete crystalline conversion from A-PD to C-PD in the bases (Nos. 2-4) containing MC and the bases (Nos.5-7) containing HPC were about 20-30 d and 3-18 d, respectively. Furthermore, in vitro release of PD from No.1 base without MC and from No.2 base containing MC were studied for 24 h after preparation at 5℃. Since A-PD was entirely converted into C-PD after 24 h at 5℃, the amount of PD released from No.1 base was less than that of immediately after preparation, whereas the release pattern of PD from No.2 base was the same as that from the base immediately after preparation since crystalline conversion did not occur in No.2 base. In addition, the release of PD from No.4 base was studied for 10 d after preparation at 5℃. The amount of PD released from No.4 base after 10 d was the same as that of immediately after preparation, since crystalline conversion of PD did not occur in this base. Water-soluble polymers such as MC and HPC act as protective colloids, and so the structure of the emulsion in the ointment base is stabilized. The structure of the emulsion in the base including water-soluble polymer is stabilized even at low temperature where the o/w type emulsion structure normally deteriorates. It is suggested that water-soluble polymer is an effective additive to o/w type ointment bases.
公益社団法人日本薬学会の論文
1982-03-25

Effects of Water-Soluble Polymers on the Crystalline Conversion of Prednisolone in Oil-in-Water Type Ointment Bases

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