"Ozone-Friendly" Alternatives to CFCs

MDIs have historically used small amounts of chlorofluorocarbons (CFCs) as the propellant which delivers medication into the lungs. CFCs have a long established record of safety in human use. In the last decade, environmental scientists discovered the connection between the use of CFCs and the destruction of the ozone layer around the earth.

When released, CFCs disperse unchanged in the lower atmosphere and rise gradually to the upper atmosphere where they remain for many years. Eventually, they are broken down by the sun’s radiation and release active chlorine which can destroy ozone molecules.

The ozone layer acts as a protective barrier between the earth’s surface and the sun. Ozone depletion was linked to increased levels of harmful UV radiation reaching the earth’s surface.

The Montreal Protocol

The consequences of ozone depletion were the topic of an international conference organized by the United Nations Environment Programme (UNEP) in 1987. A protocol to the convention, the Montreal Protocol on Substances that Deplete the Ozone Layer, called for signatory countries to phase out the production of CFCs by January 1, 1996.

The Montreal Protocol allowed for CFC production to continue for uses deemed "essential." MDIs for the treatment of asthma and chronic obstructive pulmonary diseases fall into this category.

Alternatives to CFCs for Use in Medical Inhalers

CFC-driven metered-dose inhalers have a long established record of safety and effectiveness in patient therapy. But most of the gases which are suitable for use in commercial processes as CFC replacements cannot be used in medical aerosols because of their toxicity, flammability, or for other reasons. Pharmaceutical researchers have therefore concentrated on identifying alternative propellants, for use in MDIs, with the same safety profile as CFCs.

Two CFC replacements have been developed for medical uses; they are referred to as hydrofluoroalkanes (HFAs) or as hydrofluorocarbons (HFCs), and contain only carbon, hydrogen and fluorine. They are non-flammable and chlorine-free, so they have no impact on the stratospheric ozone layer.

Pre-clinical studies have shown that HFCs are suitable alternatives to CFCs for human use.

In July 1994, the Committee for Proprietary Medicinal Products in the European Union (CPMP) stated that HFC-134a of a specified quality could be a suitable alternative to CFCs in MDIs for the treatment of asthma. The CPMP issued a similar assessment of HFC-227 in September 1995.

The first CFC-free MDI was introduced in 1995 and as of July 1999, HFC MDI products were available in at least 40 countries worldwide.

Reformulation efforts with both HFC-134a and HFC-227 are continuing, so that CFC-free MDIs can be produced for all the relevant drugs as rapidly as good science and thorough regulatory review will allow.