Aim and objectives: Serious drug interactions are amongst the common problems encountered by the anaesthesiologists in their practice that compells them to understand the effects of individual drugs and their combinations. One such drug interaction is the effect of sevoflurane and ondonsetron on QT interval when administered individually and also when combined together.The aim of the study is toevaluate the effects of Ondansetron and Sevoflurane and theirpossible synergistic effectson QT interval. The effects on QT interval were observed whenOndansetron was administered on patients undergoing Sevoflurane anesthesia using corrected QT interval (QTc) by Bazett’s formula.

Methodology: Our study was a prospective randomized double blinded study which was done to evaluate QTc interval in 150 patients, aged between 20-60 years. QT interval was corrected by using Bazett’s formulato the heart rateand are noted at various interval period such as base line(Preoperative period), 10min, 15min, and 20 mins after the administration of ondansetron using 5 lead ECG in Lead II.

Results: There was significant prolongation of QTc interval in Sevoflurane + ondansetron group (477.92 ± 11.44) when compared with placebo (448.93 ± 8.21) with p value of <0.00001.

Conclusion: Ondansetron when administered with sevoflurane significantly prolonged theQTc intervalthat was not significant enough to produce arrhythmias. Though this combination seems to be safe, one must consider caution when administering these drugs to patients with long QT syndrome or any arrhythmia along with continuous ECG monitoring