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FRIDAY, Aug. 15, 2003 (HealthDayNews) -- After years of mystery, scientists say they finally understand why asthma patients who use the most common types of inhalers often suffer from a rebound effect that makes their condition worse.
Airway-opening inhalers -- including albuterol, ventolin and salbutamol -- appear to cause a biochemical reaction that exacerbates swelling in the body's airway. The swelling, in turn, can block air flow and make breathing more difficult.
"Everyone knew that effect that was there, but no one knew why. Now we know," says Dr. Tom Stibolt, a pulmonologist with the Kaiser Permanente health plan in Portland, Ore.
Over the past two decades, a new generation of medications known as beta2-agonists, commonly found in inhalers, has let asthmatics breathe more easily by opening up their airways. But doctors have long known those patients can relapse if they don't use another kind of inhaler that reduces inflammation in the airway, which causes constriction in the first place.
On the one hand, the bronchodilating inhalers -- known as "relievers" -- are a good temporary measure "because they save lives while you do the things you need to do to reduce the inflammation," Stibolt says. But patients often are so impressed by the rapid response of the inhalers that they don't use the anti-inflammation inhalers -- known as "controllers" -- that provide a recurrence.
"They say this medication isn't doing anything," Stibolt says. "But it's preventing a problem, not relieving it. The mediations they desperately need to be on don't do anything they notice."
As the inflammation on the walls of the airway gets worse, the reliever inhalers fail to work properly as they become overwhelmed, he explains. "It actually worsens the problem in the long term."
The airway constriction can even last for weeks after a patient stops using the reliever inhalers, says Stephanie Shore, a senior physiology lecturer at the Harvard School of Public Health.
However, she adds, the number of affected patients appears to be small. Some may have inherited a propensity to develop the problem.
In the new study, researchers at the University of Cincinnati examined genetically altered mice that were designed to have different levels of a receptor that works to keep the airway open and unblocked by swelling. The results of the study appear in the Aug. 15 issue of the Journal of Clinical Investigation.
The researchers report they discovered an interaction between chemicals that contributes to the growth of inflammation.
Shore, who wrote a commentary accompanying the study, says researchers will need to turn to tests in humans to see if the findings translate to people.
For now, Stibolt says, asthma patients need to understand the importance of using both the reliever and controller inhalers. "If you're using enough controller medication, you hardly use any reliever medication," he says, adding most people should just have to use the reliever inhalers a couple of times a week.
Some patients, however, wrongly accept their poor breathing. "The problem is they don't come in and say, 'I'm using a lot of reliever mediation, help me.' They just figure that's the way it is," he says.
In a separate development, the U.S. Food and Drug Administration (FDA) on Thursday warned users of three asthma drugs that those medications carry a small risk of a life-threatening asthma attack.
The FDA found that patients taking drugs with salmeterol, a long-acting bronchodilator, were likelier -- but still not likely -- to have a dangerous asthma episode. The affected drugs are sold under the names Serevent Inhalation Aerosol, Serevent Diskus and Advair Diskus, all of which are made by GlaxoSmithKline.
The agency said the benefits of these drugs "continue to outweigh the risks when used according to the instructions," and warned of the dangers of stopping the drugs without first consulting a doctor.
More information
To learn more about asthma and medications, visit the American Academy of Allergy, Asthma and Immunology or the American Lung Association.
