Ending a 5-year debate about the appropriate use of inhaled beta-agonists in treating asthma, researchers in the National Heart, Lung, and Blood Institute's (NHLBI) Asthma Clinical Research Network (ACRN) have shown that for people with mild asthma, taking an inhaled beta-agonist at regularly scheduled times is safe but provides no greater benefit than taking the medication only when asthma symptoms occur. The scientists recommend that physicians treating patients with mild asthma prescribe inhaled beta-agonists only on an as-needed basis.
The study, which appears in the September 19th New England Journal of Medicine, also demonstrates that contrary to what some earlier studies suggested, asthma patients continue to have a good response to inhaled beta-agonists, even after months of daily use.
"This study should lay to rest the concerns of the more than 7 million Americans with mild asthma--and their physicians--about the safety and effectiveness of inhaled beta-agonists," said NHLBI Director Dr. Claude Lenfant. "For the patient with only occasional asthma symptoms, there is no reason to take medication regularly. Patients with more than occasional symptoms should contact their physicians, not use their inhaler more frequently," he said.
"Since more than half of the asthma patients in this country have mild asthma, this study should result in a substantial decrease in the overall cost of asthma care," he added. Asthma is a chronic lung disease that affects more than 13 million Americans. The frequency, severity of illness, and death rate from the disease all have been increasing steadily for more than a decade. Asthma also is a major cause of lost wages and school absenteeism, resulting in estimated annual health care costs of more than $4.6 billion.
Prior to 1990 most asthma experts believed that prescribing beta-agonists on a regularly scheduled basis improved overall control of asthma symptoms. Several studies since then have suggested that regular beta-agonist use might induce tolerance or even adverse effects, leading to diminished control of asthma in some patients, and some scientists hypothesized that this could account for the increasing asthma severity, hospitalization and death rates seen world-wide. These studies included patients with moderate, as well as mild asthma, who were using beta-agonists along with other asthma medications.
The ACRN study, conducted at 5 medical centers nationally, followed 255 patients with mild asthma, ages 12 to 55, for 6 months. After a 6-week evaluation period, patients were randomized to receive either the inhaled beta-agonist, albuterol, 2 puffs 4 times a day, or an identical-appearing placebo inhaler for 16 weeks. Patients in both groups were permitted to take additional albuterol, when needed for relief of asthma symptoms. During a final 4-week withdrawal period, all patients received only as-needed albuterol.
The study showed that even though the average use of albuterol was 5 times higher in the regular use group than in the as-needed group, there were no significant differences between the 2 groups in measures of lung function, asthma symptoms, or quality of life that could be attributed to the treatment. Although a few differences between the 2 groups could be attributed to the treatment, the effects were small and deemed to be clinically unimportant.
The Guidelines for the Diagnosis and Management of Asthma, released by the NHLBI's National Asthma Education and Prevention Program in 1991, define mild asthma as a condition in which the patient has few clinical signs or symptoms of asthma, except for occasional episodes of coughing and wheezing -- no more than 1 to 2 times a week. The Guidelines recommend beta-agonists as the treatment of choice for these episodes. If the patient begins to experience more frequent symptoms or if it appears that the beta-agonist is no longer relieving the symptoms, the patient should contact their physician.
Beta-agonists are a class of drugs that relax airway smooth muscle. They provide relief of asthma symptoms, rather than treating the underlying inflammation that produces the symptoms. Albuterol (Ventolin, Proventil) is the most commonly prescribed and used intermediate-acting beta-agonist in the U.S. The albuterol and placebo for the beta-agonist study were donated by Schering-Plough, headquartered in Kenilworth, NJ.
The NHLBI's Asthma Clinical Research Network was created in 1993 as a 5-year program to expedite design and implementation of clinical trials on approaches to managing asthma. "By putting in place a network of geographically dispersed clinical centers that conduct multiple trials in asthma patients, the Institute can facilitate the rapid evaluation of new and existing therapeutic approaches to this disease," said Dr. Lenfant.
At the time of this study, the Network was composed of investigators from the following 5 centers: Harvard Medical School; National Jewish Center for Immunology and Respiratory Medicine, Denver; University of Wisconsin, Madison; Thomas Jefferson University, Philadelphia; University of California at San Francisco. The data coordinating center is located at the Pennsylvania State University's Hershey Medical Center, Hershey, PA. A sixth center at Harlem Hospital in New York was added in 1995.