Pharmaceutically acceptable salt and polymorphic forms of flupirtine maleate

Polymorph X of flupirtine maleate characterized by data selected from the group consisting of:

• a) having an X-ray powder diffraction pattern, or substantially the same X-ray powder diffraction pattern, as shown in FIG. 5 and
• b) having characteristic X-ray powder diffraction peaks (2θ):
• 5.8±0.2°, 13.3±0.2°, 19.4±0.2°, 20.6±0.2° and 24.2±0.2°.