Aprepitant L-proline solvate compositions and aprepitant L-proline solvate cocrystals are disclosed as well as pharmaceutical compositions containing them. The compositions and cocrystals of the invention are: 1:1:1 aprepitant L-proline methanol composition; a 1:1:1 aprepitant L-proline methanol cocrystal; a 1:1:1:1 aprepitant L-proline ethanol composition; a 1:1:1 aprepitant L-proline ethanol cocrystal; 1 1:1:1 aprepitant L-proline n-propanol composition; and a 1:1:1 aprepitant L-proline n-propanol cocrystal: The aprepitant L-proline solvate compositions or cocrystals may be used in the same way as aprepitant to treat or prevent disorders relating to emesis, a neuropsychiatric disease, an inflammatory disease, pain, cancer, a skin disease, itch a respiratory disease, or an addiction.