Ondansetron (a 5HT-3 receptor antagonist) has been shown in multiple randomized controlled trials (RCT’s) and meta-analysis to inhibit activation of Bezold-Jarisch Reflex (BJR) in response to spinal anesthesia for elective cesarean section patients. Studies have not determined whether the timing of administration changes the inhibitory affect of ondansetron in this patient population. This project addressed the following question: Does administration timing of Ondansetron, a 5-HT3 receptor antagonist, affect inhibition of the Bezold-Jarisch Reflex in obstetric cesarean section patients receiving spinal anesthesia? De-identified aggregated electronic medical record data for a one-year period was obtained. Data was grouped by ondansetron administration timing prior to spinal administration: ≤ 15 minutes (G1), > 15 minutes and ≤ 30 minutes (G2), > 30 minutes (G3). Blood Pressure (BP) data, including systolic, diastolic and mean arterial pressure (MAP), was included for four time points: pre spinal, 5-, 15- and 30-minutes post spinal. Change in BP from baseline were used for analysis. Total vasopressor usage was also included for analysis. Sixty-six obstetric cases were included, (G1 n=24), (G2 n=24) and (G3 n=18). Data was analyzed using the one-way ANOVA test for BP change scores and the Kruskal-Wallis for evaluating vasopressor use. No statistical significance between groups was found in BP change scores or vasopressor use. However, G3 did show greater drops in BP and increased vasopressor usage compared to G2 and G1. Further evaluation is recommended through either a large-scale retrospective study or randomized control trial (RCT).