Some Asthma Drugs Can Endanger Patients

Two new studies reveal that regular use of beta-agonist drugs for the treatment of asthma causes tolerance to develop in patients and increases cardiac risks.

Adrenergic drugs, such as albuterol and terbutaline, work on receptors located on smooth muscles and inflammatory cells in the lungs. These bronchodilator medicines can relax the muscles around the airways that constrict during an asthma attack. Short-term use has been shown useful in reducing symptoms of acute asthma attacks. However, continuous use causes patients to develop tolerance for the drug, making them less effective in true emergencies.

Moreover, beta-agonist use in patients with asthma and chronic obstructive lung disease also increases the risk for adverse cardiac events, such as heart attacks, over twofold, compared to placebos. Beta-agonists work on receptors found in the heart, increasing the heart rate and decreasing the level of potassium, an essential element. These effects are the exact opposite those of beta-blocker drugs, such as atenolol, often used to decrease the risk for heart attacks and congestive heart failure.

One study, published in the May 2004 issue of the Annals of Internal Medicine, was a meta analysis of more than a dozen research papers. A second meta analysis that pooled the results from 33 trials on the cardiac effects of beta-agonists was published in the June 2004 issue of Chest. The researchers found that most studies showing favorable results for beta agonists were flawed. Most of them involved conflicts of interest because they were funded by pharmaceutical companies and/or because researchers had financial ties to the industry.

"We think the studies warning of adverse respiratory effects are getting lost among dozens of poor-quality studies that missed the point,” said Edwin Salpeter, Ph.D., professor of physics at Cornell University (Ithaca, NY, USA), who worked on the meta analyses along with colleagues from Stanford University (Palo Alto, CA, USA).





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