Photodecomposition after Dispensing Alfacalcidol Solution and Its Countermeasure

The photodecomposition of alfacalcidol solutions (Alfarol® solution) available in prescription and amber glass bottles (manufactured goods) was examined. Alfacalcidol solutions were stored under room light (fluorescent lighting, 940 lux) and near the north window for 28 days, and under ultraviolet lamp for 4 hours. Samples were withdrawn from each bottle at certain times and assayed by high-performance liquid chromatography. Alfacalcidol was found to be unstable under the light-unshaded condition. The Residual contents of alfacalcidol in the prescription bottles were 40% and 85% after 28 days under room light and near the north window respectively, and was 25% after 4 hours under ultraviolet lamp. Therefore, we prepared an alfacarcidol and fat emulsion mixture to increase the photostability of alfacalcidol, and noted that this mixture was stable against light. For example, the residual content of alfacalcidol in the in prescription-bottled mixture was 96% after exposure to room light in a cold place (4°C) for the 28-day period.