Controlling
Asthma cont..
Asthma attacks are
often milder than this description - just a shortness of breath that
soon passes without treatment.
But asthma attacks can also be
much, much worse, requiring a hurried trip to the hospital for
emergency--sometimes lifesaving - care. Even in severe cases, hospital
treatment usually enables asthma patients to regain near-normal
breathing. But not always. More than 5,000 asthma deaths were reported
in the United States in 1997, according to the American Lung Association
(1997 is the most recent year for which statistics are available). Most
of the deaths occurred in patients who misjudged the severity of
symptoms or failed to reach a hospital or clinic in time to prevent
respiratory failure.
Although African-Americans make up less than 13 percent of the U.S.
population, they account for nearly 22 percent of deaths due to asthma,
according to the American Lung Association.
For reasons that are not well understood, the number of newly diagnosed
cases of asthma in the United States is rising sharply, up 58.6
percent between 1982 and 1996. Asthma deaths, too, are
climbing--5,434 in 1997 compared with 2,598 in 1979. While not
accounting for the rising prevalence of asthma, the lack of necessary
health care, especially among the urban poor, may play an important role
in the rising asthma death rate.
Ironically, these increases are taking place at a time when some
irritants believed to be associated with asthma--such as air pollution,
dust, molds, and tobacco smoke--are better understood and often under
better control than they once were. The reason for the increases remains
a mystery, but some investigators think one contributing factor is
modern, tightly sealed homes and workplaces that trap and recirculate
contaminants, increasing exposure to them in the air we breathe.
Inflamed Airways
Most of America's estimated 17 million people with asthma, of whom
almost 5 million are under age 18, mildly affected. About a quarter of
asthmatic children seem to "outgrow" their disease in their teen years
or as young adults. It's not certain, however, that they are completely
free of asthma. Studies of people with late-onset asthma--asthma that
first shows up in the fifth or sixth decade of life or even later-have
found that many of them experienced asthma-like breathing difficulties
as children.
There is no known cure for asthma, but asthma often can be
well-controlled by a strategy aimed at preventing acute episodes and
halting those that do occur.
This two-pronged attack is increasingly effective because scientists are
piecing together a more comprehensive picture of the nature of asthma
and gaining new insights into the cause, prevention and management of
acute asthma attacks. New information is changing the way practicing
physicians and the Food and Drug Administration view the role of drugs
in asthma treatment and prevention.
Changing Theories
Until the 1970s and early 1980s, asthma was understood to result
from over-responsiveness of the tubes (bronchi and bronchioles) that
carry air to and from the lungs. People with hypersensitive airways,
when exposed to certain irritants called "triggers"--such as household
dust, tobacco smoke, cat fur (dander), cockroach droppings, air
pollutants, even vigorous exercise or cold air--would experience "bronchospasm,"
a narrowing of the airways caused by contraction of the muscles that
encircle the bronchial tubes.
Asthmatics also tend to produce thick, sticky mucus and have
inflamed, damaged airways, both of which worsen the breathing
restriction caused by bronchospasm. During an acute attack, asthmatics
seem to have a hard time getting their breath. Actually they are
struggling to push air out of over-inflated lungs through constricted
airways.
That understanding of asthma led to treatments aimed primarily at
opening up the bronchial tubes by using drugs that cause the bronchial
muscles to relax their grip on air passages. Bronchodilators are still a
mainstay of asthma therapy. But Robert Meyer, M.D., of FDA's Center for
Drug Evaluation and Research, notes that scientists' understanding of
asthma has changed significantly over the last decade or so.
He points out that since the early 1980s, increasing scientific evidence
shows that inflammation is as much responsible for bronchospasm as
anything else. Today, Meyer says, "putting primary emphasis on
controlling bronchospasm rather than chronic airway inflammation looks
like "putting the cart before the horse".
The evidence Meyer refers to strongly indicates that asthma is a chronic
inflammatory disease that usually develops within the first few years of
life. Much of this evidence is discussed by H.W. Kelly of the University
of New Mexico College of Pharmacy in the October 1992 issue of the
Journal of Clinical Pharmacology and Therapeutics. Kelly is a member of
FDA's Pulmonary and Allergy Drugs Advisory Committee.
In people with asthma, whether mild or severe--even in asthmatics
whose first acute attack occurs long after childhood--the air passages
are continuously inflamed, causing them to be swollen and to react
strongly to inhaled irritants. But because patients may not be aware of
any symptoms, this inflammation is sometimes called "the quiet part" of
asthma.
People with chronically inflamed airways may show no outward signs of
asthma until the first acute attack requires urgent medical
attention, often at a hospital emergency department. Emergency care
physicians and nurses--who are all too familiar with acute asthma--are
able to administer powerful drugs to open the patient's air passages and
restore more normal breathing. They are likely to recommend the patient
be seen by an asthma specialist, who can devise a combination of
treatment and prevention measures aimed at avoiding or minimizing
further acute asthma attacks. The first step in that process is an
accurate diagnosis.
Diagnosing Asthma
The diagnosis of asthma is based on repeated, careful
measurements of how efficiently the patient can force air out of the
lungs and on a thorough medical history and laboratory tests to find out
what triggers the patient's acute attacks.
People with asthma react to external irritants in a way that
non-asthmatics don't. Many, but not all, asthmatics have allergies that
cause their bodies to produce an abnormal array of chemicals in response
to environmental allergens. In that sense, asthma is akin to pollen
allergies, hives, and eczema. But in asthma, the allergic reaction
contributes to inflammation of the airways rather than of skin, eyes, or
nose and throat. An acute asthma attack may come on rapidly after
exposure to an irritant or develop slowly over several days or weeks,
which can complicate the job of identifying a patient's asthma triggers.
Which drugs asthma patients need, when to use them, and how much to use
depend largely on the character of their illness, as shown by the degree
of breathing impairment and the frequency and severity of acute attacks.
Asthma experts agree, however, that the first line of defense is
avoidance of whatever brings on an acute asthma episode. For many
patients triggers--there are often more than one--are likely to be
identified as common allergens or air pollutants. In some asthmatics,
attacks can be brought on by strenuous exercise, exposure to cold
outdoor air, industrial or household chemicals (cleaning fluids, for
example), and food additives such as sulfites. Influenza or even cold
viruses can also trigger asthma episodes. In other cases, the triggers
cannot be identified, even after a thorough investigation.
Asthma Drugs
Knowing what provokes an asthma attack is critically important in
prevention, but it's often difficult or impractical to avoid contact
with triggering irritants. Today, however, physicians can prescribe
drugs to lessen the risk of acute attacks after exposure to an offending
irritant, as well as halt attacks that can't be prevented.
The asthma drugs used to treat asthma fall into two broad
categories: controllers to prevent acute attacks and relievers that
check acute symptoms when they occur. Some drugs do both.
In light of mounting evidence that asthma is fundamentally an
inflammatory disease, asthma authorities today regard inhaled
corticosteroids--marketed under numerous brand names, including Aerobid,
Azmacort, Vanceril, Flovent and Pulmicovt--as the most effective agents
for controlling airway inflammation and thus preventing acute asthma
attacks. Corticosteroids in pill or tablet form (such as Medrol) and in
liquid form for children (such as Pediapred and Prelone) are prescribed
long-term for some patients with severe asthma, or short-term for
patients with a serious asthma episode.
Other inhaled anti-inflammatory controller drugs include Intal (cromolyn
sodium), which is useful in preventing asthma brought on by exercise,
and Tilade (nedrocromil sodium). A new class of oral anti-inflammatory
controller drugs acts by blocking a certain part of the inflammation
pathway. This class of "anti-leukotriene" drugs include Zyflo (zileuton),
Accolate (zafirlukast) and Singulair (montelukast).
Bronchodilators work to help open the breathing tubes (bronchi), but do
not treat the underlying inflammation. There are both short-acting and
long-acting bronchodilators. Long-acting inhaled bronchodilators, such
as Serevent (salmeterol), and long-acting oral bronchodilators, such as
Alupent (metaproterenol), Proventil (albuterol sulfate), Theo-24 (theophylline
anhydrous), and many others, are often used in conjunction with
anti-inflammatory agents to control symptoms. They don't provide
immediate relief of symptoms, but their preventive action persists for
many hours, which makes them useful in controlling attacks that might
occur during hours of sleep.
Drugs to bring quick relief in acute asthma attacks are chiefly
short-acting inhaled bronchodilators that act rapidly but for a
relatively brief time to relax bronchial constriction. There are many
short-acting bronchodilators to choose from, including Alupent or
Metaprel (metaproterenol), Brethaire (terbutaline), and Ventolin or
Proventil (albuterol). Although these drugs are effective in treating
asthma, there is some controversy about their safety, especially when
they are overused. Scientific debate makes it clear, however, that an
increasing need for inhaled bronchodilators, or a decreasing response to
each dose, is a signal that the patient's asthma is not being adequately
controlled. Patients who have an increasing need for short-acting
inhaled bronchodilators should be reevaluated promptly by their
physicians.
Both prescription and over-the-counter (OTC) short-acting
bronchodilators are available. Like the prescription drugs, the OTC
drugs act only to provide symptom and relief, and they are generally
effective for a shorter period. They may be useful, therefore, as
temporary treatment for mild asthma attacks. Ready availability in
drugstores makes the OTC products potentially helpful as a "stopgap" for
patients who do not have their prescription medication at hand when an
asthma attack occurs. More importantly, patients who use OTC inhalers
should still seek advice from a health professional about the long-term
treatment of their asthma.
The key to effective, long-term treatment of asthma is finding the drugs
and dosage plan most effective in dealing with or preventing acute
episodes. But effective treatment depends as well on the patient and the
care-giver knowing what the various anti-asthma drugs do, when and in
what amount each drug should be used, when a change in symptoms or in
the response to a particular drug requires a call or visit to the
physician, and when to get emergency help. Physicians who specialize in
treating asthmatics go over these points in detail as part of an overall
treatment plan designed and, as necessary, adjusted to meet the needs of
each individual patient.
A cure for asthma is judged by experts to be still a far-off
possibility. But the majority of asthma sufferers can lead essentially
normal, symptom-free lives by understanding and sticking to a
well-planned strategy to keep clear of asthma triggers and to use the
right drugs in the right way.
It isn't easy, but it works.
Ken Flieger is a writer in Washington, D.C.
Asthma Information
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