A 1:1:1 aprepitant L-proline H2O composition and a 1:1:1 aprepitant L-proline H2O cocrystal are disclosed as well as pharmaceutical compositions containing a 1:1:1 aprepitant L-proline H2O composition or cocrystal and a pharmaceutically acceptable carrier. The 1:1:1 aprepitant L-proline H2O composition or cocrystal may be used in the same way as aprepitant to treat or prevent disorders relating to emesis, a neuropsychiatric disease, an inflammatory disease, pairs, cancer, a skin disease, itch, a respiratory disease, or an addiction.