The aim is to evaluate the effectiveness of different regimens of prophylactic Ondansetron, Dexamethasone, or both, on the incidence and severity of post-operative nausea and vomiting.

Patients will be randomized to one of four arms: Ondansetron (4O-PE: 4 mg Ondansetron pre-emergence, 8O-PE: 8 mg Ondansetron pre-emergence, 4O-PI: 4 mg Ondansetron pre-incision, 8O-PI: 8 mg Ondansetron pre-incision), Dexamethasone (4D-PE: 4 mg Dexamethasone pre-emergence, 8D-PE: 8 mg Dexamethasone pre-emergence, or 4D-PI: 4 mg Dexamethasone pre-incision, or 8D-PI: 8 mg Dexamethasone pre-incision), Combination Therapy group (4O-PI+8D-PI: 4 mg Ondansetron pre-incision + 8 mg Dexamethasone pre-incision, 4O-PI+8D-PE: 4 mg Ondansetron pre-incision + 8 mg Dexamethasone pre-emergence, 4 O-PE+8D-PI: 4 mg Ondansetron pre-emergence + 8 mg Dexamethasone pre-induction, 4 O-PE+8D-PE: 4 mg Ondansetron pre-emergence + 8 mg Dexamethasone pre-emergence), and Placebo group 2 ml Saline 0.9%. Primary outcome will be the incidence of PONV in the PACU prior to discharge.

Inclusion Criteria:

• ASA grade I and II
• Aged 18-70 years
• Patients scheduled for elective surgery under general anesthesia

Exclusion Criteria:

• All patients who received antiemetics or cortisone within 48 hr before surgery
• Pregnant, breast feeding ladies
• Any patient with BMI (Body Mass Index) > 34 kg/m²
• Patient with gastrointestinal, hepatic, renal, mental or psychiatric illnesses were also excluded from the study protocol.

Adult patients undergoing elective surgery under general anesthesia