Opioids are effective analgesics, but cause side effects including sedation, respiratory depression, low blood pressure, nausea, and constipation. Gabapentin enacarbil, which is a FDA approved drug for post herpetic neuralgia (nerve pain related to shingles) and restless leg syndrome, may decrease your need for narcotics and thus decrease the risk of side effects. The investigator hopes this study will determine if gabapentin enacarbil decreases opioid consumption and pain after surgery.

Patients having elective hip and knee surgery will be asked to participate in the study. Patients will be randomized to Gabapentin enacarbil 600mg twice per day for 5 days or Placebo twice per day for 5 days.

One day prior to surgery the patient will take Gabapentin enacarbil 600mg or placebo 600mg twice a day with meals. On the day of surgery, the patient will take Gabapentin enacarbil 600mg or placebo 600mg two hours before the surgical procedure. Six hours after the completion of surgery, the patient will receive Gabapentin enacarbil 600mg or placebo 600mg. If the patient is sent home, the patient will be given 6 Gabapentin enacarbil 600mg or placebo 600mg pills to take home along with instructions. However, if the patient remains hospitalized, on the first day after the surgery, the patient will have pain assessed in the morning using a numerical rating score. The patient's quality of recovery will be evaluated using a questionnaire and the patient will receive Gabapentin enacarbil 600mg or placebo 600mg twice a day with meals. The second and third day the patient is in the hospital, the patient will have pain assessed in the morning using a numerical rating score and the patient will receive Gabapentin enacarbil 600mg or placebo 600mg twice a day with meals. Then, three months after surgery, the patient will receive a phone call to follow-up with possible pain or discomfort the patient may be feeling.

A randomized controlled trial to determine the effect of gabapentin enacarbil on opioid consumption and pain scores in patients having primary hip or knee replacement surgery with spinal anesthesia.

Screening visit

• Consent will be obtained

• Vital Signs

• Physical evaluation

• Medical History

• Laboratory values and medication checked via Epic

• Pain scores using numerical rating scores (NRS)

• Brief pain inventory (BPI)

• Randomization will be to standard management with GEn or to standard management with placebo. Patients will be given GEn 600 mg bid or placebo 600 mg bid for 1 preoperative day and will receive 600 mg GEn or placebo about 2 hours before surgery and then restarted on GEn or placebo 600 mg within 6 hours of surgery, and then 600 mg bid for three additional days.

  2 days prior to surgery Phone call will be made to remind patients to take GEn 600 mg bid or placebo 600 mg bid

  1 day prior to surgery

• vital signs

• GEn 600 mg bid or placebo 600 mg bid

• monitoring and recording of adverse events

Day of Surgery

• Medical History
• Laboratory values and medication checked via Epic
• Patients will be given GEn 600 mg or placebo single dose with sips of water 2 hours before surgery and then restarted within 6 hours of completion of surgery.
• Vital Signs
• Social history
• Demographic data to be obtained includes height (cm), weight (kg), age (yr), gender, (ASA) physical status, and self-declared ethnicity
• Individual risk for nausea and vomiting will be determined using the Apfel score.
• Monitoring and recording of adverse events
• Pain scores using numerical rating scores (NRS) during the PACU stay every 15 minutes for the first hour after surgery

POD 1

• GEn 600 mg bid or placebo 600 mg bid
• Vital Signs
• Monitoring and Recording of adverse events
• Pain scores using numerical rating scores (NRS) in the morning
• Myles QoR scale to formally evaluate quality of recovery

POD 2

• GEn 600 mg bid or placebo 600 mg bid
• Vital Signs
• Monitoring and Recording of adverse events
• Pain scores using numerical rating scores (NRS) in the morning

POD 3

• GEn 600 mg bid or placebo 600 mg bid

• Vital Signs

• Monitoring and Recording of adverse events

• Pain scores using numerical rating scores (NRS) in the morning

  3 Months after surgery

• Phone call will be made to check for any adverse event and with the intention to assess chronic pain.

• Monitoring and recording of adverse events

• Data obtained from electronic medical records will include: operation time, surgery type, intraoperative opioid consumption, postoperative opioid consumption in PACU and in ward, breakthrough pain medication requirements, pain scores in PACU and ward, requirement of antiemetics for nausea and vomiting, requirement of antihistaminic medications, requirement of laxatives for constipation, ambulation time, flatus, ileus, bowel movements, length of stay and any side effects or complications. Preoperative and postoperative laboratory data including but not limited to renal function will also be collected from electronic medical records. Patient functionality will also be recorded including, bathing, toileting, walking and moving.

Inclusion Criteria:

1. Men or women 18-85 years of age.
2. Scheduled for elective knee or hip arthroplasty with spinal anesthesia.

Exclusion Criteria:

1. Creatinine >1.50 mg/dl.
2. History of clinically important current depression or currently on any prescribed anti-depressant medication.
3. Previously enrolled in any Xenoport trial.
4. Use of gabapentin or gabapentinoids (Lyrica, Horizant, Neurontin or Gralise) within one month.
5. Allergy to gabapentin or gabapentinoids (Lyrica, Horizant, Neurontin or Gralise).
6. Women who are pregnant or breastfeeding.
7. History of seizure disorder within the last one-year or taking medications for seizures.

Initial 72 hours after surgery or until hospital discharge, whichever came first.