APPROACHES AND CHALLENGES TO USE FREON PROPELLANT REPLACEMENTS

Freon propellants commonly referred to as chlorofluorocarbons (CFCs) a re involved in the destruction of the ozone layer. The countries parti cipating 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 rep lacements for CFCs in metered dose inhalers (MDIs), which include the development of HFA-134a by IPACT-I and the development of HFA-227 by I PACT-II. Neither of these replacement propellants contains chlorine so they have no potential to destroy ozone. In addition, each of these n ew propellants has less global warming potential than currently used C FCs. The IPACT organizations have comprehensive testing programs devel oped from consultation with global regulatory authorities. These progr ams are largely complete with respect to subchronic evaluations and cu rrent work is focused on long-term evaluations. Results have indicated that the new propellants are extremely benign and have an equal or be tter safety profile than the CFCs they are meant to replace. With the safety of the new propellants becoming more evident with time, new for mulations 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 formu lations. Comparison studies have shown that the safety profile of the new formulations is not different from that of the CFC formulations. I n summary, the availability and desirability of the use of CFCs in MDI s is limited. Fortunately several alternative propellants to the CFCs are approaching development finalization. The testing program has show n that these replacements are acceptable from a safety assessment pers pective and their introduction will assure that vital MDI therapy will continue uninterrupted.