The study included 60 patients at high risk for PONV (Apfel-score 0, I, II, III and IV) scheduled for elective laparoscopic surgeries at the Central Surgical Center of Irmandade da Santa Casa de Misericórdia in São Paulo. Inclusion criteria will be ASA I or II of either sex, in the age range of 18 to 70 years. In this study, the recruited patients will be allocated randomly into three groups. The group A will receive oral 600 mg gabapentin 2 h before surgery. The group B will receive oral 150 mg pregabalin 2 h before surgery. The Group C will receive oral placebo 2 h before surgery and ondansetron 8mg intravenous at the end of the surgery. This study is "double-blind", in which neither the doctor nor the patient knows what medicine is being given.