Provided herein are compositions comprising a dextromethorphan analog according to Formula I or Formula II or a pharmaceutically acceptable salt of either of the foregoing and a co-agent, eg., an antidepressant such as a serotonin norepinephrine reuptake inhibitor a serotonin noradrenaline dopamine reuptake inhibitor a norepinephrine dopamine reuptake inhibitor a monoamine oxidase inhibitor a selective serotonin, reuptake inhibitor and a tricyclic antidepressant or a pharmaceutically acceptable salt of any of the foregoing. The compositions are useful in the the treatment of pseudobulbar affect, neuropathic pain, neurodegenerative diseases, brain injuries, and the like.
