Disclosed herein are methods of administering relatively high doses of dexmedetomidine or a pharmaceutically acceptable salt thereof to a human subject, without also inducing significant sedation. The disclosed methods are particularly suitable for the treatment of agitation, especially when associated with neurodegenerative and/or neuropsychiatric diseases such as schizophrenia, bipolar illness such as bipolar disorder or mania, dementia, depression, or delirium.