HFA-propelled albuterol safe for patients, Ozone.
However, the hydrofluoroalkane (HFA)-propelled drug penetrates deeper into the lower lung, which causes a greater peak in plasma concentrations. This increases the likelihood of heart rate increases in patients using lower doses of albuterol, Dr. Adam Wanner said at the annual meeting of the American College of Allergy, Asthma, and Immunology.
"With the HFA propellant, you get a slightly higher tachycardic response that takes off sooner than what you see with CFC [chlorofluorocarbon] propellants," said Dr. Wanner, Joseph Weintraub Professor of Medicine, Pediatrics, and Biomedical Engineering at the University of Miami. At higher doses, however, the albuterol-induced tachycardia is equivalent between the formulations, he added.
The difference in lung penetration is due to the particle size each propellant delivers. HFA delivers a significantly smaller particle, with more of it deposited in the lower lung. "The device delivers the same amount of drug, but because it has greater penetration, you will see higher plasma concentrations for a short period of time," he explained.
According to an international policy set by the Montreal Protocol on Substances that Deplete the Ozone Layer, a United Nations environment program, all developed countries must phase out CFCs by 2010. Medical aerosol propellants are a secondary target of the phase-out, which initially concentrated on CFCs in refrigeration. In the United States, the phase-out goal is Jan. 1, 2008. "After that, no CFC-propelled aerosol will be allowed in the U.S.," said Dr. Wanner, who also serves on the United Nations' Medical Aerosol Technical Options Committee.
The data supporting the safety of switching propellants in albuterol are robust, collected from more than 20 studies, Dr. Wanner said. One of the most important investigations examined the switch to HFA-propelled albuterol among nearly 10,500 asthma patients in Great Britain. The prospective trial, which documented safety and short- and long-term efficacy over 1 year, found no increase in major or minor adverse events following the introduction of the HFA-powered inhaler (Int. J. Clin. Pharmacol. Ther. 2003;41:67-76).
A Texas study examined efficacy in more than 300 asthma patients who switched to HFA-propelled albuterol. Patients maintained pulmonary function and other measures of asthma control at levels comparable with baseline. Treatment was well tolerated, and the adverse event profile was similar to that of CFC-propelled medication. There were no clinically relevant effects on electrocardiography, vital signs, or lab values (Ann. Allergy Asthma Immunol. 2001;86:297-303).
Studies have also shown equivalency and safety in children and in patients with exercise-induced bronchoconstriction, Dr. Wanner said.
European countries are far ahead of the United States in phasing out HFA propellants in medical aerosols, he added. Many have opted for dry-powder inhalers rather than HFA propellants. All studies comparing the three formulations have concluded that there are no differences among them in safety or efficacy.
But only 20% of U.S. inhalers are dry-powder formulations, below the global average of 27% and far below the average in many other countries, including Japan, where dry-powder formulations account for 60% of inhalers, and Scandinavia, where 90% of inhalers are dry powder.
Leading up to 2008, the United States has had a linearly decreasing metric tonnage exemption for medical aerosols. In 1995, the exemption was 40,000 metric tons, he said. In 2007, the exemption will be less than 2,000 metric tons. After 2008, the annual exemption will be about 350 metric tons.
BY MICHELE G. SULLIVAN
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|Title Annotation:||Pulmonary Medicine|
|Author:||Sullivan, Michele G.|
|Publication:||Internal Medicine News|
|Date:||Dec 15, 2006|
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