Effect of Gabapentin Enacarbil on Opioid Consumption and Pain Scores

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

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

Exclusion criteria

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