Memantine for Post-Operative Pain Control

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).

7 days prior to surgery, start taking 5mg memantine daily; 4 days prior to surgery, increase dose to 5mg twice daily; 2 days prior to surgery, increase dose to 10mg in the morning, and 5 mg in the evening; on the day of surgery, increase dose to 10mg twice daily, and continue on this dose until 14 days after surgery.

7 days prior to surgery, start taking one placebo tablet daily; 4 days prior to surgery, increase dose to one placebo tablet twice daily; 2 days prior to surgery, increase dose to 2 placebo tablets in the morning, and one placebo tablet in the evening; on the day of surgery, increase dose to 2 placebo tablets in the morning and 1 placebo tablet in the evening. On the first day after surgery through 14 days after surgery, take 1 placebo tablet twice daily.

Treatment group differences in side effects (nausea, itching, sedation, urinary retention following foley catheter discontinuation)

Changes in pain and quality of life questionnaire responses (SF-McGill-2, Brief Pain Questionnaire, SF-36 v2)

Inclusion Criteria: Surgery for total hip replacement, knee replacement OR lumbar spinal fusion Taking no opiate medication OR taking opiate medication for at least 6 weeks Exclusion Criteria: History of alcohol or drug abuse Clinical diagnosis of Alzheimer's Disease Prior adverse reaction to memantine Severe renal impairment (creatinine clearance <30 ml/min) Inability to give informed consent

Grande LA, O'Donnell BR, Fitzgibbon DR, Terman GW. Ultra-low dose ketamine and memantine treatment for pain in an opioid-tolerant oncology patient. Anesth Analg. 2008 Oct;107(4):1380-3. doi: 10.1213/ane.0b013e3181733ddd.