The impurities in Fluothane: their biological properties.

Fluothane (halothane BP), one of the purest anaesthetics, contains traces of some impurities amounting to a total of 005 per cent w/w, none of them exceeding 001 per cent w/w. Once these impurities had been identified they were synthesized and tested for anaesthetic activity and toxicity. The results of these experiments showed that most of these impurities have low toxicity but Fluothane contains traces of four unsaturated hydrocarbons that are relatively toxic. When Fluothane is administered in anaesthetic concentrations, its impurities are diluted to the same extent and therefore cannot be administered in toxic concentrations.