Etomidate (ETO) is a synthetic imidazole-based anesthetic widely used for the induction of general anesthesia due to its rapid onset of action and short duration of action. From a chemical structure perspective, it is known as 1-(1-Phenylethyl)imidazole-5-carboxylic acid ethyl ester and exists in two enantiomers due to the presence of one carbon chiral centre near the methyl group. Its molecular formula is C₁₄H₁₆Nâ‚‚Oâ‚‚ with a molecular weight of 244.293 g/mol, as shown in Figure 1. It occurs as a white crystalline powder or a clear, colorless solid, with a melting point between 69–70°C. It has low water solubility and is usually formulated in propylene glycol solution. Etomidate is a high-value chemical that can be produced at high yield rates.

Figure 1: Chemical structure of (-)-Etomidate, the (S) isomer

(+)-Etomidate isomer acts by stimulating γ-aminobutyric acid (GABA) receptors, causing sedation. The anesthetic effect occurs within 30–60 seconds and lasts for 4–8 minutes before it is metabolized in the liver and plasma through the ester hydrolysis process. Although very useful in medicine, its pharmacological properties also make it potentially abused due to certain side effects.

Since 2022 until now, etomidate has been detected in blood, urine, liver, kidney and hair using sensitive analytical techniques such as LC–MS/MS. Analysis of hair samples allows for the detection of its history of use.

There is only one scientific report from China that found etomidate was detected in all electronic cigarette (e-liquid) samples analyzed. However, this issue has attracted attention in Malaysia as the issue of vaping and the chemicals in it is being hotly debated by various parties.

Currently, the Malaysian Ministry of Health is considering listing etomidate under the Dangerous Drugs Act 1952 following a proposal in the Dewan Rakyat. Currently, etomidate is listed under the Poisons Act 1952, Group B for clinical use only.

Dr. Mohd Rashidi Abdull Manap AMRSC, FSSM is a faculty member at the Department of Chemistry, Universiti Putra Malaysia (UPM). In addition, he is a Visiting Research Fellow at Lund University, Sweden, currently based at BMC - Biomedicinskt Centrum.

Date of Input: 05/08/2025 | Updated: 05/08/2025 | adib.yusof