The present invention provides novel polymorphs of (3S,11aR)-N-[(2,4-difluorophenyl) methyl]-6- hydroxy-3-methyl-5, 7-dioxo-2, 3,5,7, 11, 11a-hexahydro[1, 3]oxazolo[3, 2-a]pyrido[1, 2-d]pyrazine-8-carboxamide including sodium and potassium salts and pharmaceutical compositions containing these polymorphs. Also provided are methods for making the novel polymorphs.La présente invention concerne de nouveaux polymorphes de (3S,11aR)-N-[(2,4-difluorophényl) méthyl]-6- hydroxy-3-méthyl-5, 7-dioxo-2, 3,5,7, 11, 11a-hexahydro[1, 3]oxazolo[3, 2-a]pyrido[1, 2-d]pyrazine-8-carboxamide comprenant des sels de sodium et de potassium et des compositions pharmaceutiques contenant ces polymorphes. Linvention concerne également des procédés de préparation de nouveaux polymorphes.
