The present invention addresses the problem of providing a
medicine that, despite of being a non-ergot
dopamine agonist (DA), reduces the risk of the drowsiness
side effect, and exhibits an excellent
therapeutic effect on neurodegenerative disorders such as Parkinson's
disease (PD). The present invention relates to a pharmaceutical composition for treating neurodegenerative diseases such as Parkinson's
disease, the pharmaceutical composition comprising 1-{[(4aR,6R,8aR)-2-amino-3-cyano-8-methyl-4,4a,5,6,7,8,8a,9-octahydrothieno[3,2-g]quinolin-6-yl]carbonyl}-3-[2-(dimethylamino)ethyl]-1-propylurea or a pharmacologically acceptable salt thereof. The pharmaceutical composition is characterized by being orally administered at a daily
dose of 0.25 mg to 2 mg in terms of
free form.