Introduction to Etomidate
Etomidate is a short-acting intravenous anesthetic agent primarily used for the induction of general anesthesia and for procedural sedation [1.5.8]. First developed at Janssen Pharmaceutica in 1964 and introduced clinically in Europe in 1972, it has a long history of use [1.3.3, 1.5.8]. As a carboxylated imidazole derivative, its primary advantage is its remarkable cardiovascular stability, making it a preferred agent for patients who are hemodynamically unstable, such as those with decreased myocardial contractility, hypovolemia, or severe cardiac disease [1.3.2, 1.3.3]. Unlike many other induction agents, etomidate causes minimal changes to heart rate, blood pressure, and cardiac output [1.3.2, 1.3.7].
Is There Another Name for Etomidate?
Yes, there are other names for etomidate. While 'etomidate' is the generic name for the drug, it is most commonly marketed in the United States under the brand name Amidate [1.2.4, 1.3.5]. In Europe, another formulation is known as Hypnomidate® [1.2.3]. The drug is also available as a lipid emulsion called Etomidate-Lipuro, which is associated with less pain upon injection compared to the standard formulation dissolved in propylene glycol [1.2.3, 1.3.3]. Therefore, when clinicians refer to Amidate, they are speaking about the specific brand formulation of etomidate [1.2.4].
Mechanism of Action
Etomidate exerts its hypnotic (sleep-inducing) effects by acting on the central nervous system. It is a positive allosteric modulator of the gamma-aminobutyric acid type A (GABA-A) receptor, which is the main inhibitory neurotransmitter system in the brain [1.3.3, 1.3.6, 1.3.7]. By enhancing the effect of GABA, etomidate increases the flow of chloride ions into neurons. This action leads to hyperpolarization of the neuron, making it less likely to fire and thus depressing brain activity, which results in sedation and anesthesia [1.3.2, 1.3.6]. It has a rapid onset of action, typically within one minute, and a short duration of 3 to 10 minutes, making it ideal for procedures like rapid sequence intubation (RSI) [1.3.2, 1.6.9]. It's important to note that etomidate provides hypnosis but has no analgesic (pain-relieving) properties [1.3.2, 1.3.7].
Key Side Effects and Clinical Concerns
Despite its hemodynamic benefits, etomidate's use is tempered by several significant side effects.
Adrenocortical Suppression
The most notable and controversial side effect of etomidate is its transient inhibition of adrenal steroid synthesis [1.5.6]. Even a single induction dose can block the enzyme 11-beta-hydroxylase for 6 to 12 hours [1.3.7, 1.5.6]. This enzyme is critical for the production of cortisol, a vital stress hormone [1.3.3]. This suppression prevents the body from mounting a normal stress response, a major concern in critically ill or septic patients [1.5.6]. Because of this effect, etomidate is not used for continuous infusion for long-term sedation [1.3.7].
Myoclonus
Another very common side effect is myoclonus, which are involuntary muscle spasms or jerks that can occur during induction [1.3.6]. The incidence is reported to be between 30% and 80% in patients who have not been pre-medicated [1.3.7, 1.5.4]. While generally harmless, these movements can be disruptive during delicate procedures [1.5.7]. The exact cause is thought to be related to a disinhibitory effect on parts of the nervous system that control motor activity [1.3.7].
Other Side Effects
- Pain on Injection: Many patients experience pain or a burning sensation at the IV site. This is more common with the propylene glycol formulation (Amidate) than the lipid emulsion version (Etomidate-Lipuro) [1.3.3, 1.5.8].
- Postoperative Nausea and Vomiting (PONV): The incidence of nausea and vomiting after surgery is higher with etomidate compared to other agents like propofol [1.5.1, 1.5.8].
Comparison with Other Anesthetic Agents
Etomidate is often compared to other common induction agents like propofol and ketamine. Each has a unique profile that makes it suitable for different clinical scenarios.
| Feature | Etomidate (Amidate) | Propofol (Diprivan) | Ketamine (Ketalar) |
|---|---|---|---|
| Hemodynamics | Very stable; minimal effect on blood pressure [1.3.2] | Causes vasodilation and hypotension (low blood pressure) [1.6.4, 1.6.6] | Stimulatory; increases heart rate and blood pressure [1.2.1] |
| Respiratory Effect | Minimal respiratory depression [1.3.2] | Significant respiratory depression; can cause apnea [1.2.1] | Bronchodilator; respiratory drive generally maintained [1.6.9] |
| Analgesia | None [1.3.7] | None [1.2.7] | Potent analgesic (pain relief) [1.6.9] |
| Key Side Effect | Adrenal suppression, myoclonus [1.5.6] | Hypotension, pain on injection [1.6.4, 1.5.8] | Emergence reactions (hallucinations, dysphoria) [1.6.9] |
Conclusion
To answer the question, "Is there another name for etomidate?"—the most prevalent name in clinical practice is its brand name, Amidate [1.2.4]. Etomidate holds a crucial, albeit niche, role in modern anesthesiology. Its unmatched hemodynamic stability makes it an invaluable tool for inducing anesthesia in the most critically ill patients [1.3.4]. However, its use requires careful consideration due to the significant and well-documented risks of adrenocortical suppression and myoclonus [1.3.7, 1.5.4]. The choice between etomidate and alternatives like propofol or ketamine depends entirely on the patient's individual clinical condition, the procedural requirements, and the practitioner's judgment.
