To rebalance the study plan because it is not desirable to set up comparators using placebo.

Hyperalgesia is known to be caused by the excitatory amino acid through NMDA receptor. GABA, an inhibitory amino acid, alters the opioid receptor sensitivity against pain resulting hyperalgesia. If the GABA level can be maintained at certain level, the progression into hyperalgesia can be averted. GABA related drugs are known to decrease the postoperative opioid consumption, lower the degree of pain, and prevent hyperalgesia. We hypothesize the effective postoperative pain management and the prevention of hyperalgesia from pregabalin, GABA analogue, and the possible sex difference in such effects of pregabalin.

Inclusion Criteria:

• 18, <51 years

  • healthy patients accepted for video-assisted living donor nephrectomy

Exclusion Criteria:

• Female patients who are pregnant or menopause
• Patients undergoing hormonal therapy
• Patients having neurologic disease or already taking GABA related drugs (pregabalin, gabapentin), or taking opioid drugs
• Insulin resistant diabetes
• Renal deficiency (eGFR < 60 ml/min/1.73 m2)
• Emergency operation, hemodynamically unstable patients
• Foreigner
• allergic to medication given in this study