The stability of hydrocortisone-17-butyrate (HC-17-B) in the admixture of Locoid®, Ointment with Anderm® Ointment (AO), zinc oxide (10%) ointment (ZO) or Juvela® Ointment (JO) was investigated by the quantitative analysis using high performance liquid chromatography. The decomposition routes of HC-17-B to hydrocorisone-21-butyrate (HC-21-B) and hydrocortisone (HC) in such ointment admixtures were also investigated.
In the stability test, percentages of the residual active HC-17-B and decomposition products in the admixtures immediately after mixing and after 2, 4, 8 and 12 weeks of storage in darkness at 5°C, 25°C or 40°C were investigated. As a result, it was found that the admixture with AO of a white petrolatum base was stable under any of the storage conditions. In the admixture with ZO, HC-17-B was stable at 5°C but it decomposed after storage at 25°C or higher temperature, resulting in the formation of HC-21-B and HC. In the admixture with a JO of o/ w type hydrophilic ointment base, HC-17-B decomposed under any of the storage conditions, and with the rise in storage temperature the level of HC-17-B decreased quickly while the level of HC-21-B increased rapidly first, then decreased slowly with the gradual increase in the level of HC.