Arthroscopic shoulder rotator cuff repair is associated with severe postoperative pain. The interscalene block (ISB) is commonly used for this type of surgery, providing analgesia by anesthetizing the nerves that supply the shoulder. Although the nerve block provides extremely effective analgesia for the first 6-8 hours, patients experience severe pain once its effect has regressed. This study will assess whether a single dose of oral hydromorphone controlled release, given to overlap the waning of the ISB, will improve postoperative pain control and reduce the incidence of rebound pain.