Approaches and Challenges to Use Freon Propellant Replacements

Freon propellants commonly referred to as chlorofluorocarbons (CFCs) are involved in the destruction of the ozone layer. The countries participating in the Montreal Protocol voted in 1990 to require a phase-out of CFC production by the year 2000. In 1992, the phase-out was moved forward to 1996. There are two pharmaceutical consortia evaluating replacements for CFCs in metered dose inhalers (MDIs), which include the development of HFA-134a by IPACT-I and the development of HFA-227 by IPACT-II. Neither of these replacement propellants contains chlorine so they have no potential to destroy ozone. In addition, each of these new propellants has less global warming potential than currently used CFCs. The IPACT organizations have comprehensive testing programs developed from consultation with global regulatory authorities. These programs are largely complete with respect to subchronic evaluations and current work is focused on long-term evaluations. Results have indicated that the new pro-pellants are extremely benign and have an equal or better safety profile than the CFCs they are meant to replace. With the safety of the new propellants becoming more evident with time, new formulations of existing aerosol drugs are being developed. This testing includes stand-alone safety evaluations as well as studies of the drug in new propellant formulations directly compared to current CFC formulations. Comparison studies have shown that the safety profile of the new formulations is not different from that of the CFC formulations. In summary, the availability and desirability of the use of CFCs in MDIs is limited. Fortunately several alternative propellants to the CFCs are approaching development finalization. The testing program has shown that these replacements are acceptable from a safety assessment perspective and their introduction will assure that vital MDI therapy will continue uninterrupted.