The property of being highly lipid-soluble means that the induction agents cannot readily be presented as aqueous solutions.

Propofol is an emulsion containing 1% propofol in a lipid medium.

Thiopental is a weak acid and can be dissolved in water as long as it is mainly in the ionized form, i.e. when the pH is very high. Therefore, it is stored as its sodium salt, as a powder mixed with sodium carbonate, so that when 20 ml of water is added it produces a 2.5% solution of thiopental with a pH of 10.5.

Etomidate is soluble, but is stabilized by 35% propylene glycol to give a 0.2% solution.