Introduction: Intraoperative nausea and vomiting (IONV) and Post operative nausea and vomiting 
(PONV) one of the most distressing anaesthesia-related adverse effects. Aim of the work: The 
present study aims to evaluate the prophylactic effect of intravenous ondansetron and dexamethasone 
on decreasing the incidence of nausea and vomiting in parturients undergoing elective caesrean 
section under spinal anaesthesia. Patients and methods: After approval of the university ethical 
committee and obtaining informed consent from all patients. This prospective, double-blinded study 
was conducted in gynecology and obstetric department, El-Minia University Hospital during the 
period from October 2018 to October 2019, after obtaining approval from the ethical committee and 
verbal consent from the patients. A total of one hundred and fifty women in child bearing period (18-
45 years) , with BMI of 23-27, height of 150-170 cm and ASA physical status II, who were candidate 
for elective caesarean, were enrolled in this prospective randomized study. patients were randomly 
allocated into three groups, 50 patients in each one. Each patient in this study received 5 min 
preoperatively one of the syringes which containing either: Group A: IV ondansetron 8 mg diluted in 
5 ml normal saline. Group B: IV dexamethasone 8 mg diluted in 5 ml normal saline. Group C: 5 ml 
normal saline The following variables (SBP, DBP, MAP, HR, SpO2) were recorded just before 
medications (baseline) and intraoperatively also nausea and vomiting was recorded. post operative 
nausea and vomiting were recorded up to 4 days . Results: Ondansetron and dexamethasone decrease 
incidence of Nauesa and vomiting. Conclusion: IV administration of 8 mg of ondansetron or 8 mg 
of dexamethasone 5 minutes before operation were effective in decreasing the incidence of Nauesa 
and vomiting.