SUMMARY: Many drugs administered to patients in the perioperative period  are known to prolong Qtc like thiopentone, inhaled anaesthetics, ondansetron. Therefore we aimed to study ondansetron induced QT interval changes with isoflurane and halothane in healthy subjects undergoing general anaesthesia.

54 patients were divided randomly into three groups. Group C (control) received ondansetron, Group H (halothane) received ondansetron and halothane, Group I (isoflurane) received ondansetron and isoflurane. QTc and haemodynamic parameters were measured at baseline, immediately after giving ondansetron and five minutes (post induction) after giving ondansetron.

 Five minutes after giving ondansetron there was a statistically significant prolongation of the QTc interval (QTc3) in Group C and Group I as compared to baseline (QTc1). QTc3 in group I showed statistically significant prolongation as compared to the group H.

So, concomitant use of isoflurane and ondansetron  may prolong the QTc, predisposing to the development of arrhythmias.