Pain is a common element of surgery. Opiates (morphine, oxycodone, hydrocodone, methadone,
fentanyl) are very helpful in decreasing pain after surgery. Unfortunately, with repeated use
opiates lose their effectiveness, such that patients need to utilize more opiates to achieve
adequate pain relief - a phenomenon called tolerance. Sometimes tolerance to a pain
reliever's effects can develop in just a few hours. It is thought that activation of the
N-methyl d-aspartate (NMDA) receptor, a "switch" found on the surface of nerves, is partially
responsible for opiate tolerance. Memantine is a medication that limits the activity of NMDA
receptors in the brain and spinal cord. It has been used for years to help patients with
Alzheimer's Disease. In this study, we will study the effects of memantine when combined with
opiate medications to see whether it can increase the effectiveness of opiates for pain after
surgery and reduce the side effects caused by opiates (e.g., sedation, nausea, itching).