PROBLEM TO BE SOLVED: To provide a preventing or therapeutic agent for prostatomegaly.SOLUTION: The preventing or therapeutic agent for prostatomegaly contains, as effective components, an α lipoic acid derivetive represented by formula (1) (wherein R represents an amino acid residue bonded with a nitrogen atom or a peptide residue bonded with a nitrogen atom and M represents a pharmacologically permissible metal other than palladium) or its pharmacologically permissible salt or their solvate.COPYRIGHT: (C)2012,JPO&INPIT【課題】前立腺肥大症の予防または治療剤を提供すること。【解決手段】次の式(1)で示されるαリポ酸誘導体、その薬理学的に許容される塩またはそれらの溶媒和物を有効成分とする前立腺肥大症の予防または治療剤。【選択図】なし