The present application relates methods for treating a depressive symptom comprising administering an effective amount of a μ opioid receptor agonist or a pharmaceutically acceptable salt thereof to a subject in need thereof. Non-limiting examples of such agonist include the compounds of Formulas I, II, III, and IV, as well as the compounds of Table A.
The invention provides compounds that are chemically modified by covalent attachment of a water-soluble oligomer. A compound of the invention, when administered by any of a number of administration routes, exhibits characteristics that are different from those of the compound not attached to the water-soluble oligomer.