This article is from the Asthma FAQ, by Patricia Wrean and Marie Goldenberg email@example.com with numerous contributions by others.
As you may know, CFC (chlorofluorocarbon) chemicals, which are used as
propellants in aerosol products including asthma inhalers (MDIs), damage
the ozone layer. As a result, there has been a worldwide ban on the
production of these chemicals for all but essential uses.
Products which relied on CFCs, such as air conditioning units,
refrigerators, and most aerosol products, have been modified to use
alternative chemicals which do not damage the ozone layer. Due to their
nature, however, metered dose inhalers have been granted an "essential
use" exemption to the worldwide ban, which grants the manufacturers an
extra few years to develop alternatives.
Since the inactive ingredients (i.e., everything but the drug itself)
must be changed, it's not as simple as using a different chemical for the
propellant - the new device must go through much the same approval
process as the original inhaler did, to ensure that the same dosage is
delivered to the patient, that there are no side effects, that patients
tolerate the new formulation well, etc.
The FDA has already approved one new non-CFC inhaler, Proventil HFA
(albuterol), which uses hydrofluoralkane instead of CFC propellants.
Other non-CFC devices are currently in the works. It is expected that
future non-CFC inhalers may be reviewed and approved more quickly than
the earlier ones.
CFC-based MDIs will continue to be available for some time. Proposed
guidelines for final phaseout include that there be at least 3 multi-use
(see below) non-CFC devices available in a drug class (i.e.,
bronchodilators, corticosteroids), providing at least 2 different drugs,
before all CFC inhalers in that class are banned. As an example,
CFC-based bronchodilators would be permitted as long as Proventil HFA is
the only alternative; if Ventolin (also albuterol) and Alupent
(metaproterenol) had non-CFC versions, then all CFC formulations might be
The term "multi-use" refers both to aerosol inhalers and multi-use
dry-powder inhalers such as the diskhaler. It does not include
single-use dry-powder inhalers such as the rotahaler, which requires
insertion of a new capsule of medication with each use.