Induction Agents

Induction Agents

What is an induction agent?

Induction agents are drugs used to induce and maintain general anaesthesia. Usually the term induction agent refers to the intravenous agents described below, however it is possible to do a gas induction using a volatile anaesthetic agent as well, so they can also technically be included as induction agents.

Objectives of this section

  • Recall the pertinent chemical, pharmacokinetic and pharmacological properties of Propofol, Ketamine, Thiopentone, Etomidate and Midazolam
  • Compare and contrast the properties of these drugs and their clinical uses in anaesthetic practice
  • Use this knowledge and understanding to select an appropriate induction agent for various clinical scenarios


  • The most commonly used agent
  • Usually a 10mg/ml lipid emulsion
  • Well tolerated, and contrary to popular believe, it can be given to patients with an egg allergy, because the constituent in propofol is from the yolk, and the allergens are in the egg white



  • NB. Thiopentone can be used as an IV infusion for Cerebral Protection, but for the purposes of Anaesthesia is only used as an induction bolus.



  • Note that while midazolam is a benzodiazepine, it can also be used as an induction agent
  • It is also commonly used as a pre-medication and anxiolytic

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