| abstract |
An injectable anaesthetic formulation comprises a halogenated anaesthetic compound, such as desflurane, isoflurane, enflurane, halothane or sevoflurane, but preferably isoflurane, and at least one emulsifier, preferably soybean oil. Although not essential, it is preferred to also include lecithin (an emulsifier also) and a co-emulsifier such as a polyoxyethylene-polyoxypropylene block copolymer, for example, poloxamer 188. The composition may further contain water, a pH adjustment agent, such as sodium hydroxide, and/or glycerol. It is preferred that the halogenated anaesthetic has a boiling point between 20{ and 60{C. An example of such a formulation comprises isoflurane (10 ml); soybean oil (10 ml); glycerol (2.5 g), lecithin (1.8 g) and water (q.s.). The proportion of anaesthetic to emulsifier should be, at a minimum, 1 part emulsifier to 3 parts anaesthetic in order to ensure the formation of a stable emulsion. The total amount of dispersed non-aqueous phase (anaesthetic plus emulsifier(s)) should be less than or equal to about 32% v/v in order to provide a solution of suitable viscosity for administration by injection. |