A finely particulate medicinal preparation in which a drug can be more stably present as micelle type fine particles； and a method of stabilizing fine particles or a finely particulate medicinal preparation. The finely particulate medicinal preparation comprises a surfactant such as an ascorbic acid derivative or phospholipid derivative and a drug. It can be used as, e.g., a drug for intravenous injection. The method of stabilization comprises incorporating an ascorbic acid derivative into either fine particles made of a surfactant or a finely particulate medicinal preparation comprising the fine particles and a drug incorporated therein to thereby stabilize the fine particles or the finely particulate medicinal preparation.
