Shaking Off the Shakes: Study evaluates Ondansetron's Role in Mitigating Etomidate-Induced Myoclonus

Myoclonus following etomidate administration is a prevalent complication, occurring in 50-80% of untreated patients receiving the anesthetic. As etomidate is commonly used for rapid induction of anesthesia due to its cardiovascular stability, recently published study aimed to assess ondansetron's effectiveness in reducing these involuntary movements, considering its known mechanisms involving serotonin and GABA receptors.

Methodology

A double-blind clinical trial was conducted involving 72 adult patients (ASA I-II) undergoing elective eye surgeries at Khatam Al-Anbia Eye Hospital. Patients were randomly assigned to two groups: one receiving 4 mg of ondansetron and the other receiving normal saline (placebo), both prior to etomidate induction (0.3 mg/kg). Myoclonus severity was graded as mild, moderate, and severe based on observed movements. The primary outcomes included the presence, severity, and duration of myoclonus, while secondary outcomes considered demographic factors like age and gender. Statistical analyses were performed using SPSS, with differences assessed using chi-square tests, t-tests, and Mann-Whitney tests.

Key Results

The results indicated a significant reduction in myoclonus duration and severity among the ondansetron group. Specifically, myoclonus duration averaged 5.75 ± 14.07 seconds in the ondansetron group compared to 53.17 ± 43.48 seconds in the placebo group (Z=-5.19, P < 0.005). Furthermore, myoclonus occurrence was significantly lower (χ² = 14.62, P < 0.005) and its severity was reduced in the ondansetron group (χ² = 25.89, P < 0.005). No significant variation was noted in vital signs between both groups post-intervention, suggesting that ondansetron did not adversely affect hemodynamic stability.

Limitations

Despite its novel findings, the study had several limitations. It did not explore the dose-dependent effects of ondansetron or compare it with other antiemetic agents like granisetron. Additionally, while factors like age, gender, and ASA class showed no correlation with myoclonus occurrence, the study did not investigate potential interactions with other medications that patients may have received prior to surgery.

Overall, the findings support ondansetron's potential as a safe adjunct in reducing etomidate-induced myoclonus, proposing further research to solidify dosage considerations and comparative efficacy with other agents.

Key Points

• Prevalence of Myoclonus: Myoclonus following etomidate administration is a frequent complication, occurring in 50-80% of patients who do not receive treatment, highlighting a significant concern in anesthetic practice.

• Study Design: A double-blind, randomized clinical trial was conducted with 72 adult patients undergoing elective eye surgeries. Participants were divided into two groups: one received 4 mg of ondansetron and the other a normal saline placebo before etomidate induction at a dose of 0.3 mg/kg.

• Primary Outcomes: The primary outcomes were focused on myoclonus, including its presence, severity, and duration. Severity was categorized as mild, moderate, or severe, and demographic variables such as age and gender were considered as secondary outcomes.

• Reduction of Myoclonus: The ondansetron group exhibited a notable reduction in both the duration and severity of myoclonus, with an average duration of 5.75 seconds compared to 53.17 seconds in the placebo group, indicating a statistically significant difference (Z=-5.19, P < 0.005).

• Hemodynamic Stability: There were no significant changes in vital signs between the ondansetron and placebo groups following the intervention, suggesting that ondansetron does not negatively impact cardiovascular stability during anesthesia inductin.

• Study Limitations: Limitations included the lack of assessment for dose-dependent effects of ondansetron and absence of comparisons to other antiemetics such as granisetron. Furthermore, demographic factors did not correlate with myoclonus incidence, and potential interactions with other preoperative medications were not explored, which warrants further investigation.

Reference –

Mohammad Alipour & S. Firuzabadi (2025). Investigating The Effect Of Ondansetron In Reducing Myoclonic Movements Caused By Intravenous Administration Of Etomidate. *BMC Anesthesiology*, 25. https://doi.org/10.1186/s12871-025-03099-7.