This study, therefore, aimed to investigate the effect of intraperitoneal administration of ondansetron in combination to lidocaine for postoperative pain management in patients undergoing lower abdominal cancer surgery.

Postoperative pain relief is very important issue in any surgery. The common postoperative pain management is traditionally based on opioids (1,2). Considering opioids' adverse effects such as nausea, vomiting, sedation, drowsiness, and urinary retention, recently there is a lot of interest for f inding a safe and effective pain treatment after operation. Local anesthetics intraperitoneal instillation is recognized as a useful technique for postoperative pain management. They can reduce inflammatory response after surgery and produce analgesia by blocking neural transmission at the site of tissue injury (5). 5-HT3-antagonists, including ondansetron, are commonly used as anti-emetics to prevent and treat chemotherapy-induced vomiting and nausea [7]. Several studies have shown that 5-HT3-antagonists pose anti-inflammatory and analgesic properties, suggesting a potential clinical role in pain management.

Inclusion Criteria:

• ASA I-II patients
• scheduled for major lower abdominal cancer surgeries.

Exclusion Criteria:

• patients with known allergy to the study drugs,
• significant cardiac, respiratory, renal or hepatic disease,
• body mass index (BMI) ≥30 kg/m2;
• allergy to study drugs
• history of opioid use for pain management the time of enrolment or drug addiction,
• who had used benzodiazepine chronically,
• stroke or psychiatric disease that could affect the perception of pain.