An oral capsule formulation of a traditional Chinese herbal medicine with potential analgesic activity. In addition to other herbs, seeds and fruits, blue citrus-based herbal capsule contains the Chinese herb blue citrus (qing pi), which is produced from the dried immature green peel of the tangerine Citrus reticulata Blanco. Blue citrus contains large amounts of limonene, citral and synephrine, which may attribute to its analgesic activity. However, due to the complexity of its chemical components, the exact mechanism of action of this agent remains to be determined.