Abstract: Provided herein are transdermal delivery devices comprising dextromethorphan. The transdermal delivery device can be characterized by the novel design, for example, with an adhesive layer and a reservoir layer, with an adhesive layer comprising a mixture of two adhesives, and/or with a skin permeation enhancer, e.g., in an amount that can significantly enhance the flux of dextromethorphan. The transdermal delivery device can also be characterized by its in vitro and/or in vivo release profile, for example, that can provide a desired pharmacokinetic profile described herein. Also provided herein are methods of administering dextromethorphan, and methods of treating a disease or disorder described herein, using the transdermal delivery device herein.