Inhaled respiratory medications and the use of chlorofluorocarbons (CFCs). Thoracic Society of Australia and New Zealand.
OBJECTIVE
To assess the use of chlorofluorocarbons (CFCs) in metered-dose aerosols against the background of community concerns regarding the adverse environmental effects of CFCs.


METHODS
Data on the constituents of currently available metered-dose aerosols were supplied by the manufacturers, and details of chemistry and safety were obtained from monographs and papers published in the medical literature.


METHODS
Five papers, published in the early 1970s when metered-dose aerosols first became popular, were reviewed for safety data on CFCs. Several chapters in monographs were searched for data on the nature and function of CFCs in metered-dose aerosols, and five papers were the source of information on alternatives to CFCs as vehicles for the delivery of inhaled respiratory drugs.


RESULTS
The medical use of CFCs accounts for only 1.5% of the total production in Australia, the majority being used for refrigeration, air-conditioning and other commercial or industrial purposes. The physicochemical properties of CFCs are such that they function as a suitable storage medium for active drugs within the canister and as an ideal vehicle for drug delivery. Approximately 20 s after inhalation of a clinically recommended dose of a bronchodilator metered-dose aerosol, CFCs are detectable in the blood, but the concentrations decline rapidly (half-life less than 40 s). Although CFCs have been shown to sensitise the myocardium to the arrhythmogenic effects of catecholamines in experimental animals, the requisite concentrations can only be achieved by patients if they inhale from a canister on every breath for approximately 20 successive breaths.


CONCLUSIONS
CFCs used in metered-dose aerosols are an effective storage medium and a convenient vehicle for drug delivery. They are non-toxic--unless amounts far in excess of the clinically recommended doses are used, when arrhythmogenic effects may occur. The medical use of CFCs has minimal environmental impact compared with their industrial and commercial use. Dry powder delivery systems offer an alternative approach, and future research will yield nonozone-depleting CFCs suitable for replacing those in current metered-dose aerosols.
Pierce
R J
RJ
Repatriation General Hospital, Heidelberg West, Vic.
Seale
J P
JP
Ruffin
R E
RE
D000280:Administration, Inhalation; D000336:Aerosols; D001993:Bronchodilator Agents / Q000008:administration & dosage*; D005617:Chlorofluorocarbons, Methane / Q000494:pharmacology; D006801:Humans; D012140:Respiratory Tract Diseases / Q000188:drug therapy*
D000336:Aerosols; D001993:Bronchodilator Agents; D005617:Chlorofluorocarbons, Methane