Imidazole Induction Agent

Etomidate

Brand names: Hypnomidate

Etomidate is an intravenous hypnotic agent used for the induction of general anaesthesia, valued for its relative cardiovascular stability.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 0.3 mg/kg (range 0.2 to 0.6 mg/kg)

Route: Intravenous (IV route only)

Frequency: Induction of anaesthesia, injected over a period of 30 to 60 seconds

Dose must be individualised in each case. Smaller supplemental increments may be given during short operative procedures to supplement subpotent agents such as nitrous oxide; not recommended for longer procedures. Geriatric patients may require reduced doses. Concomitant IV fentanyl and other neuroactive drugs may alter dosage requirements.

Paediatric dose

Dose: 0.3 mg/kg

Route: Intravenous

Frequency: Induction of anaesthesia, over 30 to 60 seconds

Max: Range 0.2 to 0.6 mg/kg

Only in children above the age of ten (10) years, where the dose is the same as for adults (0.2 to 0.6 mg/kg, usual 0.3 mg/kg). Induction in patients below age 10 is not recommended (inadequate data).

Dose auto-extracted from US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Patient weight (kg)

Verify in a children's formulary

Contraindications

Hypersensitivity to etomidate

Side effects

Transient venous pain on injection (about 20% of patients; less with larger proximal veins)
Transient skeletal muscle movements including myoclonus (about 32%; reduced when 0.1 mg fentanyl given immediately before induction)

Clinical monograph

How it works

It produces rapid-onset hypnosis predominantly by enhancing inhibitory GABA-A receptor activity in the central nervous system.

Prescribing in practice

Even a single induction dose suppresses adrenocortical steroid synthesis, so it is not used for maintenance or prolonged sedation and is used with caution in critically ill or septic patients.
It frequently causes pain on injection and involuntary muscle movements, and is associated with a high incidence of postoperative nausea and vomiting.
It has minimal analgesic effect, so analgesia must be provided separately, and offers relative haemodynamic stability useful in cardiovascularly compromised patients.

Monitoring

Monitor level of consciousness, oxygenation, ventilation and cardiovascular parameters during induction and recovery.

Counselling the patient

Warn the patient that injection may sting and that brief muscle twitching can occur.
Ensure the team is aware adrenal suppression precludes repeated or infusion use.

Evidence & guidelines

Concern over adrenal suppression with etomidate, particularly in critical illness, is well documented in the anaesthetic and intensive-care literature.

Reference: CORTICUS Study (Sprung et al, NEJM 2008); Miller's Anaesthesia; RCoA RSI Guidelines; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

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