1. Clinical Overview
Etomidate is a potent, ultra-short-acting, non-barbiturate intravenous hypnotic agent used for the induction of general anesthesia. It is characterized by rapid onset, short duration of action, and remarkable hemodynamic stability, making it particularly valuable in patients with compromised cardiovascular function, the elderly, and those in shock. It is a carboxylated imidazole derivative.
| Onset | Duration | Bioavailability |
|---|---|---|
| Within 30-60 seconds after intravenous injection. | Approximately 3-5 minutes for a single induction dose. | 100% (Intravenous administration). |
2. Mechanism of Action
Etomidate acts as a positive allosteric modulator of the gamma-aminobutyric acid type A (GABA-A) receptor. It enhances inhibitory neurotransmission by potentiating GABA-induced chloride ion influx, leading to neuronal hyperpolarization and depression of the central nervous system (CNS).
3. Indications & Uses
- Induction of general anesthesia
- Rapid sequence intubation in emergency settings
4. Dosage & Administration
Adult Dosage: Induction: 0.2 to 0.6 mg/kg IV (typically 0.3 mg/kg). Average dose for a 70kg adult: 20mg (10ml) IV over 30-60 seconds. Titrate to effect.
Administration: For IV use only. Must be administered by a trained anesthesiologist or critical care physician. Administer as a slow IV injection over 30-60 seconds into a large vein to minimize pain. Pre-treatment with an opioid (e.g., fentanyl) or lidocaine can reduce injection pain and myoclonus. Incompatible with many other IV drugs; flush line before and after administration.
5. Side Effects
Common side effects may include:
- Pain on injection (up to 80% of patients)
- Transient skeletal muscle myoclonus (30-60%)
- Nausea and vomiting (post-operative)
- Transient apnea
- Hiccups
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Fentanyl, Midazolam, Propofol | Potentiation of hypnotic and respiratory depressant effects. Dose reduction required. | Major |
| CNS Depressants (Alcohol, Opioids, Benzodiazepines) | Additive CNS depression. | Major |
| Succinylcholine | May increase incidence and severity of myoclonus. | Moderate |
| Ketamine | May provide hemodynamic stability but increased risk of emergence reactions. | Moderate |
| Drugs inhibiting CYP450 enzymes | Potential increase in etomidate levels (theoretical). | Minor |
7. Patient Counselling
- Do inform your anesthesiologist about all medications, allergies, and medical history.
- Do fast as instructed prior to elective surgery.
- Don't drive, operate machinery, or make important decisions for at least 24 hours post-procedure.
- Don't consume alcohol for 24 hours after administration.
8. Toxicology & Storage
Overdose: Profound CNS and respiratory depression, cardiovascular collapse, apnea, prolonged coma. Effects are extensions of pharmacological action.
Storage: Store below 25°C. Protect from light and freezing. The solution is clear and colorless. Do not use if discolored or if particulate matter is present. For single use only; discard any unused portion.