The present invention relates to an infusion preparation which is useful for neurodegenerative diseases, which comprises (2R)-2-propyloctanoic acid or a salt thereof and a basic metal ion which is supplied from a metal salt or a metal hydroxide of weak acid, preferably about 1 to about 5 equivalents of a basic metal ion based on 1 equivalent of (2R)-2-propyloctanoic acid or a salt thereof, and optionally further comprises other infusion components. The infusion preparation of the present invention is has a pH appropriate for intravenous administration, and is useful for intravenous administration since it does not require any preparative operation such as dissolution, dilution or the like at the time of use.