Ondansetron, a selective serotonin 5-HT3 receptor antagonist, is well known for its antiemetic effects. However, its ability to reduce hypotension during spinal anesthesia has recently sparked great interest. In clinical practice, administering ondansetron before spinal anesthesia has produced promising results.

This prospective randomized double-blinded controlled study will be conducted on 46 patients undergoing inguinal herniorrhaphy at Suez Canal University Hospital and will be randomly assigned to one of the two groups using a table of random numbers. Group A (23 patients) will be administered 8 mg of ondansetron diluted in 100 ml of normal saline, starting with the skin preparation for spinal anesthesia through the intravenous axis to be finished in 10 minutes. Group B (23 patients) will be administered 100 ml of normal saline, starting with the skin preparation for spinal anesthesia through the intravenous axis, to be finished in 10 minutes.

Inclusion Criteria:

• Patients scheduled for inguinal herniorrhaphy in Suez Canal University Hospitals
• Height: 150 to 180 cm.
• Body mass index (BMI): not more than 35 kg/m².
• Patients are ASA I (American Society of Anesthesiology physical status Grade I) = (normal healthy patients), ASA II (American Society of Anesthesiologists physical status Grade II) = (patients with mild systemic disease and no functional limitations).

Exclusion Criteria:

• Patients refused to participate in the study.
• Contraindications of spinal anesthesia.
• Known allergy to bupivacaine or ondansetron.
• Patients with a history of arrhythmia, especially those with prolonged QT intervals.