The present invention relates to a medicament which is useful for neurodegenerative diseases, which comprises about 1 to about 5 equivalents of a basic metal ion based on 1 equivalent of (2R)-2-propyloctanoic acid or a salt thereof, which is supplied from a metal salt of weak acid or a metal hydroxide, and optionally further comprises an additive. The medicament of the present invention is a medicament which a pH of suitable for intravenous administration, is resistant to fluctuations of the pH and is not clouded when it is dissolved in an infusion, and an injection and the like can be prepared therefrom by using any dissolving liquid and/or dilution liquid.