Etomidate is a highly potent and primarily hypnotic drug. The substance acts on the so-called GABA receptors and the formatio reticularis (diffuse neuron network) in the human brain. This induces sleep without having an analgesic (i.e. painkilling) effect. Etomidate is one of the anesthetics and is administered to cause a comatose state to perform surgery (anesthesia).
What is etomidate?
Etomidate is a hypnotic substance used in human medicine. Preparations containing the substance cause a sleep state without having an analgesic effect. That is, sleep is induced without the silencing of any pain. Due to its effect, etomidate belongs to the class of anesthetics. It is therefore administered prior to surgery to induce deep sleep, which in turn ensures that the treatment proceeds properly (induction of anesthesia). Etomidate achieves its effectiveness by acting on the GABA receptors and the formatio reticularis in the human brain. The substance is marketed in Germany under the trade names Etomidate Lipuro and Hypnomidate. In chemistry and pharmacology it is described by the chemical molecular formula C 14 – H 16 – N 2 – O 2 . This corresponds to a moral mass of 244.29 g/mol. Etomidate is usually administered parenterally, as is common for an anesthetic, i.e., the drug is injected. The otherwise colorless, yellowish or crystalline substance with no particular odor is therefore usually traded as a solution.
Pharmacological action
Etomidate acquires its hypnotic effect by affecting GABA receptors in the human brain. Approximately one minute after administration of an injection of the drug, unconsciousness occurs in the treated individual. Depending on the dose, the duration of the effect is between 5 and 15 minutes. Multiple administration may therefore be appropriate. It is important to note that etomidate alone does not produce complete anesthesia. This is because the substance itself does not inhibit pain, which is, however, essential for performing surgery. Complete anesthesia, which is characterized by an absolute loss of sensation (especially pain), is achieved only by combining it with other anesthetics or analgesics. Etomidate does not affect the heart or circulation as much as other drugs in the same drug group. Cardiac output usually increases slightly after etomidate administration because of a slight decrease in peripheral resistance. However, respiratory minute volume decreases after etomidate administration. Therefore, when a continuous infusion is performed, respiratory depression may develop. In addition, the drug lowers the function of the adrenal cortex. However, the condition triggered by this is reversible (i.e., can be reversed). In some patients, myoclonias occur after administration of etomidate. These are brief uncontrolled twitches of the muscles. They are often suppressed by administration of opioids (e.g., fentanyl). The half-life of etomidate is 2 to 5 hours. If opioids are administered, there is a prolongation of the half-life. Metabolism of the substance occurs predominantly by the liver. Degradation is renal (via the kidney) and fecal (through feces and urine).
Medical application and use
Etomidate belongs to the group of anesthetics because it induces a sleep state. It is therefore administered exclusively for induction of anesthesia. It is used primarily in high-risk patients (ASA 3 and up according to the ASA risk classification) because it is low impact on the heart compared with other anesthetics. Nevertheless, cardiac impairment cannot be completely ruled out even when etomidate is administered. Since etomidate has no analgesic effect, it can be used to induce complete anesthesia only in combination with analgesic drugs (e.g., opioids). These are usually administered together with etomidate anyway, because the active ingredient can cause involuntary muscle twitches (myoclonias), which can be suppressed by opioids.
Risks and side effects
Because etomidate is an anesthetic, it should only be used by a specially trained physician. This person must be proficient in endotracheal intubation, which is the case with anesthesiologists.The active substance must not be administered if there is a known hypersensitivity. Since etomidate passes into breast milk, breastfeeding must not be resumed until 24 hours after administration. In pregnancy, the drug should be administered only in absolutely exceptional cases. Etomidate may cause side effects. In particular, respiratory and circulatory impairment may occur, which is typical for anesthetics. The side effects occur at different statistical frequencies:
- Involuntary muscle movements (myoclonia) occur very frequently (in at least one in 10 people treated). However, these are usually suppressed by the administration of opioids.
- Blood pressure drop and respiratory depression, nausea, and vomiting may also occur frequently (in fewer than 1 in 10 but more than 1 in 100 people treated). However, these are usually due to the administration of an opioid.
- Occasionally (in less than one in 100 but more than one in 1,000 treated), chills may occur.
- Very rarely (in less than one in 10,000 treated), hypersensitivity reactions and tonic-clonic convulsions.
