The present invention relates to crystalline forms of (1r,4r)-6'-fluoro-N,N-dimethyl-4-phenyl-4',9'-dihydro-3'H-spiro[cyclohexane-1,1'-pyrano[3,4,b]indol]-4-amine, pharmaceutical compositions and medicaments comprising these modifications, the use of these modifications as well as to a process for the enrichment of them.L'invention concerne des formes cristallines de (1r,4r)-6'-fluoro-N,N-diméthyl-4-phényl-4',9'-dihydro-3'H-spiro[cyclohexane-1,1'-pyrano[3,4,b]indol]-4-amine, des compositions pharmaceutiques et des médicaments contenant ces modifications, l'utilisation de ces modifications, ainsi qu'un procédé d'enrichissement associé.