The application is directed to Pyridone-sulfone morphinan analogs compounds of Formula I: or pharmaceutically acceptable salts and solvates thereof, wherein ==, R1, R2, R3, R4 and Z are as defined as set forth in the specification. The invention is also directed to use of the compounds of Formula I or the pharmaceutically acceptable salts and solvates thereof to treat disorders responsive to the odulation of one or more opioid receptors, or as synthetic intermediates. Certain compounds of the present invention are especially useful for treating pain.