Investigating the effect of ondansetron in reducing myoclonic movements caused by intravenous administration of etomidate.

Background: Etomidate is a short-acting intravenous anesthetic used to induce general anesthesia. However, myoclonus caused by the administration of etomidate is seen in 50-80% of untreated patients. Due to the high prevalence of myoclonus following etomidate injection, the present study aimed to investigate the effect of ondansetron in reducing myoclonic movements caused by the intravenous administration of etomidate.

Method: The current research was a double-blind clinical study conducted on 72 adult patients who were candidates for elective eye surgery and had visited Khatam Al-Anbia Eye Hospital affiliated to Mashhad University of Medical Sciences between November to December 2022. Before sampling, the designed proposal was approved by the Ethics Committee of Mashhad University of Medical Sciences and clinical trial was registered by the code IRCT20190510043545N2 at 2021-10-02. Candidate patients for elective eye surgery with ASA class I-II were selected using the available sampling method. Prior to study entrance the study protocol was fully explained and an informed constant was obtained from each participant. The patients were randomly assigned into two groups; 4 mg (IV) ondansetron was prescribed for the study group and 5 cc of normal saline (IV) was administered for the placebo group. The mentioned drugs were administered as a pre-medication 180 s before etomidate induction with a dosage of 0.3 mg/kg. After examining and recording the induced myoclonus, a full dose of narcotics and muscle relaxants was prescribed for each patient.

Results: Each group consisted of 36 patients who did not differ significantly in terms of age, gender, comorbidities and ASA class. The mean time of myoclonus in the placebo and ondansetron groups was 43.48 ± 53.17 and 14.07 ± 5.75, respectively, which was significantly shorter in the ondansetron group (Z=-5.19, P < 0.005). The severity (χ2 = 14.62, P < 0.005) and incidence (χ2 = 25.89, P < 0.005) of myoclonus were also significantly lower in the ondansetron group compared to placebo.

Conclusion: The administration of ondansetron in combination with etomidate can have a remarkable effect on reducing the duration and severity of myoclonus induced by etomidate.