This open label investigation is to determine whether cardiopulmonary bypass affects plasma gabapentin concentration after preoperative administration in the setting of cardiac bypass surgery. Following signed informed consent, 16 patients scheduled for cardiac bypass surgery will be given gabapentin (600mg, oral) 1 hour prior to surgery, 1 hour following extubation and then every 8 hours for a total of 4 doses. Plasma gabapentin levels will be measured prior to induction, prior to bypass, 10 min into the bypass procedure, 10 minutes before separation from bypass, 30 minutes following bypass and then before and 2 hours following each of the next 3 doses of gabapentin. Pain scores, sedation scores, side effects and morphine equivalents will be documented for one day following surgery.

Inclusion Criteria:

• scheduled for cardiac bypass surgery involving median sternotomy and CPB
• signed informed consent

Exclusion Criteria:

• history of chronic pain
• regular opioid consumption
• regular anticonvulsant consumption
• regular gabapentin or pregabalin use
• recent congestive heart failure
• ejection fraction <35%
• chronic pulmonary disease
• liver disease
• renal insufficiency (preoperative creatinine > 140umol/L
• history of adverse reaction to acetaminophen