An overview of the toxicology of HFA-134a (1,1,1,2-tetrafluoroethane).

1. This paper reviews the results of preclinical toxicology studies on HFA-134a carried out by Glaxo Research and Development Ltd. 2. A comprehensive range of studies was conducted in animal models suitable for the type of investigation. 3. The inhalation route of administration was used in all in vivo studies (with the exception of local tolerance and sensitisation studies) as patients will be exposed only to vapour during actuation of metered-dose inhalers. Cell cultures used for in vitro studies were also exposed to the vapour. 4. There was no mortality of rodents or dogs at extremely high vapour concentrations (81%v/v) 5. HFA-134a was considered not to be toxic or oncogenic and to provide a safe alternative to chlorofluorocarbons for use in pharmaceutical metered-dose inhalers.