Solid forms of (1r,4r)-6&prime-fluoro-N,N-dimethyl-4-phenyl-4&prime,9&prime-dihydro-3&primeH-spiro[cyclohexane-1,1&prime-pyrano[3,4b]indol]-4-amine and sulfuric acid such as (1r,4r)-6&prime-fluoro-N,N-dimethyl-4-phenyl-4&prime,9&prime-dihydro-3&primeH-spiro[cyclohexane-1,1&prime-pyrano[3,4b]indol]-4-amine sulfate or hemi-sulfate, particularly crystalline forms and/or amorphous forms thereof, pharmaceutical compositions and medicaments containing these solid forms, the use of these solid forms, and a process for obtaining such solid forms.