The combination of (a) dextromethorphan or a pharmaceutically acceptable salt thereof, precursors or derivatives, e.g. dextromethorphan hydrobromide and in particular dextromethorphan hydrobromide monohydrate； and (b) quinidine or a pharmaceutically acceptable salt thereof, precursors or derivatives, e.g. quinidine sulfate and in particular quinidine sulfate dihydrate
Dextromethorphan in combination with a CYP2D6 inhibitor can be used to treat pseudobulbar affect, emotional lability, neuropathic pain, a neurodegenerative disease, a neurodegenerative condition, a brain injury, chronic pain, intractable coughing, sexual dysfunction, dematitis, or tinnitus.
