Simultaneous quantification of acidic and basic flupirtine metabolites by supercritical fluid chromatography according to European Medicines Agency validation.

•SFC enables simultaneous quantification of acidic and basic metabolites of flupirtine.•Polysaccharide-phases show higher selectivity than traditional Si-modifications.•Specific retention of flupirtine on Lux-Amylose-2 involves halogen and π-π-bonding.•Validated SFC (guideline-conform) is suitable for clinical metabolism studies.•Oxidative degradation products comprise up to 25% of renal flupirtine elimination.