Postoperative nausea and vomiting (PONV) is commonly accompanied in patients undergoing surgery under general anesthesia. The patients undergoing laparoscopic gynecologic surgery have multiple risk factors for developing PONV such as female gender, nonsmoker, postoperative opioids, and laparoscopic surgery. Thus, it is important to prevent PONV in these patients.

Magnesium is a N-methyl-D-aspartate (NMDA) antagonist that is known to be effective in reducing opioid consumption and controlling postoperative pain. This opioid reducing effect can be associated with reduction of the incidence of PONV. However, the effect of magnesium on preventing PONV have not been investigated before. Thus, the investigators hypothesized that intraoperative infusion of magnesium will be effective in preventing PONV in patients undergoing laparoscopic gynecologic surgery.

Inclusion Criteria:

• Gynecologic disease
• Female patients undergoing laparoscopic gynecologic surgery and receiving postoperative fentanyl based intravenous patient controlled analgesia (PCA), aged 20-65 years.

Exclusion Criteria:

• impaired renal or hepatic function (Glutamic Oxalacetate Transaminase [GOT]/Glutamic Pyruvate Transaminase [GPT]>50, estimated glomerular filtration rate [eGFR]<60)
• atrioventricular block, myopathies, diabetes, treated with calcium channel blockers
• History of receiving antiemetics within 1 day before surgery
• History of receiving opioids or non-steroidal anti-inflammatory drugs within 1 week of surgery
• drugs or alcohol abuse
• patients treated with isoniazid, chlorpromazine, or digoxin
• patients who cannot communicated with others or with cognitive dysfunction
• patients who cannot read informed consent