Objectives: This study aimed to investigate the effect of preoperative prescription of two drugs Celexib and Peregabalin on postoperative pain after Orthopedic surgery is performed on volunteer patients. Study design: Randomized, double-blind, placebo-controlled, single-center, two trials study. Study setting and conduct: Before entering the operating room, patients are randomly with table of random numbers divided into three groups Celexib, peregabalin and placebo, as we do without any premedication to patients such as: Morphine, fentanyl, benzodiazepine, and so on. After referring to the ward, three hours before surgery, one patient is placed randomly in Celexib group with dose of 200 mg, one patient is placed randomly in Peregabalin group with dose of 150 mg and one patient is placed randomly in the placebo group with dose of 10 ml of normal saline 0.9%intravenously through an Angiocatheter. The method of injection and maintenance of anesthesia for all patients is the same. Presence or absence of pain in all three groups is investigated by an experienced person who is not aware of the type of drug by filling out the questionnaire, according to the pain score that stated in the questionnaire, at the end of specific time in recovery room, i.e. 45 minutes after regaining consciousness as well as, three hours after entering the ward. Participants including major eligibility criteria: Volunteer Orthopedic surgery patients between 18 and 65 years. Major exclusive criteria: People under 18 and over 65 years; Drug addicts; Diabetics; Patients with Cardiovascular Disorders; Patients who are taking Steroids for any reason; Patients who are taking Nonsteroidal anti-inflammatory drugs ongoing; Pregnant women; Patients who are taking Antidepressant and Antipsychotic drugs; Patients with fractures of the femor and pelvis.Sample: Three groups of 40 patients each. Interventions: Prescription of Celexib in one group, Peregabalin in another group and 0.9% Normal saline in the third group before surgery in order to evaluate postoperative pain in each group. The intervening time: Three hours before entering to Operation room. Variables of main outcome: Pain is as the independent continual variable and drug is as the independent nominal variable.