Gabapentin Regimens and Their Effects on Opioid Consumption

The purpose of this study is to determine the best strategy of administering gabapentin in connection with our current approach to perioperative pain management. We aim to evaluate two different adjunct gabapentin regimens given in the perioperative period, and to identify which manages patient pain more effectively and safely. In this evaluation, we will identify the quantity of patients' opioid consumption, the quality of their pain management, and the frequency and severity of any side effects they might experience. The target enrollment is 68.

Patients who are undergoing total knee replacement (TKR) at Brigham and Women's Hospital will be informed about the study and asked whether they would like to participate. Upon agreement, a patient will sign his/her consent and will be assigned to a treatment group. Patients in group 1 (the control group) will receive the standard of care as pertains to gabapentin. This consists of a single 600 mg dose of gabapentin administered to the patient approximately one to two hours before surgery, then a dose of 600 mg each morning during postoperative admission. Patients in Group 2 will receive 600 mg preoperatively, plus an additional postoperative gabapentin regimen: they will take 300 mg of gabapentin every 8 hours for 1 week, then a single nightly dose of 300 mg for another month.

Every patient being discharged from the hospital will receive from the nursing staff verbal and written instructions - the latter of which will be either printed or in electronic form - about narcotic medications. The instructions will explain when to use such medications and how to taper off their consumption. Following discharge, patients will take gabapentin as directed by their discharge instructions, and in the process track their opioid consumption on their own in their diaries. They will also document their pain, nausea and satisfaction levels according to the visual analogue scale (VAS). At the first post-operative appointment, patients' levels of opioid use will be verified and compared to the amount recorded in each diary; the actual number of tablets consumed will be compared with the documented amounts and with the prescriptions they received. Patients receiving a new prescription will also receive a matching diary for the total length of opioid treatment, including further directions on how to wean themselves off their medications. Outcome measures will be collected at both post-operative visits, the first occurring 8-10 days after surgery and the second 2-3 months following. Additional data including length of stay, postoperative complications including infection and readmission, Emergency Department visits, and routinely collected postoperative functional outcome measures (PROMs) will be recorded.

The Principal Investigator (PI) will review all drug consumption data and patient-reported outcome measures with the research assistant (RA) on a monthly basis as it is collected. The PI will participate in the collection of outcome data at the first and second postoperative visits. Data which could indicate a potential complication, whether related to the study or not - such as heightened risk of adverse outcomes or non-compliance with the tracking diary - will be addressed by the PI immediately. The PI will determine if the study should be altered in any way or stopped for safety reasons. Reasons for stoppage include a rate of adverse events greater than 10% in either group. Adverse events of primary concern include:

• Excessive sleepiness
• Allergic reactions to the opioid medications or gabapentin

All adverse events are recorded in an adverse event log, which will be kept by the RA throughout the study. The PI will review the data on a monthly basis, as well as whenever the RA alerts the PI to any potential adverse event. These checks will help to ensure validity and patient safety. Unanticipated problems will be reported to the PHRC in accordance with PHRC guidelines.

Inclusion criteria

• At least 18 years of age
• Receiving surgery for total knee replacement (TKR)
• Opioid naïve
• Agrees to use tracking diary to monitor opioid consumption

Exclusion criteria

• Over 75 years of age on the date of surgery
• If female, pregnant
• Has received investigational articles < 30 days prior to enrollment or is currently receiving investigational products or devices
• Chronic pain syndrome
• Taking chronic narcotics and/or taking more than 10 mg of codeine per day, any amount of Hydrocodone, over 200 mg of tramadol per day, or any other narcotics prescribed for moderate or severe pain
• Involved in pain clinics for chronic pain, or pain that is not related to the surgical site
• On long-term gabapentin regimen
• Taking Lyrica or Gralise
• Known history of depression or has been treated for depression with medication
• Has entertained suicidal thoughts and behaviors