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There are two main types of asthma drugs, short-acting
or quick-relief medications (also called "rescue" drugs),
and long-term control drugs.
The most common method of delivering asthma medications is through the
use of inhalers. It is important to know that not all inhalers are
short-acting drugs; in many cases long-term control drugs are also
delivered using an inhaler. To treat an occasional asthma attack, you'll
use a short-acting drug. If you only have occasional symptoms, this
may be the only type of medication you need, but even people with moderate
to severe asthma need to keep a quick-relief drug handy in case of an
attack.
Long-acting drugs, including some kind of inhalers, are used to control
and prevent symptoms in people with persistent asthma (who have symptoms
at least twice a week). The recommended dose may change over time, depending
on how severe your asthma is. These drugs are usually anti-inflammatory,
working to prevent the immune reactions that cause asthma symptoms in
the first place.
Quick-relief-acting drugs and how they work:
(See Table 1)
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Quick-relief drugs are bronchodilators - they usually
work on the nervous system's autonomic (involuntary) nerve pathways,
causing them to relax the muscles in the airways. They work by mimicking
other chemicals that would normally act on these types of nerves; specifically,
they bind to a nerve receptor to either intensify a natural reaction
or block it. (A receptor is a type of gateway or "docking station"
that only certain chemicals can fit into).
Beta-2 agonists: These are the most common quick-relief asthma
medicines. An agonist is something that "turns on" a reaction
when it lands in the right place - it's the opposite of an antagonist.
Beta-2 agonists are a class of chemicals that include adrenaline, which
controls your body's responses to stress. Beta-2 agonists bind in the
tissues around your airways, and this sets off a reaction that relaxes
the muscles in
your bronchial tubes and helps you breathe easier. Short-acting inhaled
beta-2 agonists start to work within 5 minutes and the effects can last
up to 3-8 hours. You can use it as symptoms appear, and about 20 minutes
before exercising to prevent exercise-induced asthma symptoms. (There
are also longer-acting forms used for long-term control.)
Side effects of inhaled beta-2 agonists are usually milder than
the oral form used for long-term control. Common side effects of the
inhaled form include shakiness (tremors), faster heart rate, restlessness,
anxiety, sleeplessness, headache, and muscle cramps. Different drugs
have slightly different sets of side effects.
Cautions: If you overuse this type of drug, that's a sign that
you may need more controller medication, without which your asthma symptoms
may get worse instead of better. Be sure to let your doctors know if
you have a history of angina, heart disease, high blood pressure, stroke
or seizure, diabetes, thyroid disease, prostate disease, or glaucoma.
Interactions: Other drugs may increase the effects of oral beta-2
agonists, including certain antidepressants, thyroid drugs, other bronchodilators
(oral or inhaled), and antihistamines. If you're also taking methylxanthines
(see below) for long-term control, you may feel more of the effects
on your heart. Beta blockers, used to treat heart disease, can decrease
the effect of these drugs. Oral beta-2 agonists, in turn, can interfere
with drugs that reduce blood pressure and with digitalis drugs, used
to treat congestive heart failure and very rapid heartbeat.
Anticholinergics: These drugs work by blocking a type of acetylcholine
receptor in the tissues of the lungs, which causes bronchial muscles
to relax and reduces the amount of mucous produced. Anticholinergics
work through the cholinergic branch of the involuntary nervous system,
which in conjunction with the autonomic nervous system controls your
heartbeat, breathing, and other core "housekeeping" activities.
This type of asthma medication comes in an inhaler and is usually used
in conjunction with other medicines for severe asthma attacks because
it takes longer to act. It can be used as the primary reliever medication
for some patients with chronic obstructive pulmonary disease (COPD)
like emphysema, or for those who have post-infectious cough. (It's also
used for long-term asthma control sometimes, but it's not common.)
Side effects are uncommon and usually mild. The most common ones
include dry mouth, blurred vision, sensitivity to light, and throat
or mouth irritation.
Cautions and interactions: This medication has no known drug
interactions.
Oral Corticosteroids: While they don't provide quick relief,
oral corticosteroids (a class of anti-inflammatory drugs) are sometimes
used to stabilize symptoms when an asthma attack strikes. Corticosteroids
interfere with inflammation, which is often the immune system's natural
response to an irritant or invader. For this reason, a course of corticosteroid
pills is often recommended to fight inflammation.
Long-term asthma controller drugs and how they work:
(See Table 2)
Asthma is now understood to be a chronic inflammatory disorder of the
airways in which many types of cells play a role.
Controller drugs are usually anti-inflammatory - they help to control
the immune reactions that cause asthma attacks, thus preventing them
from happening at all. Some long-acting bronchodilators are also used
for long-term control.
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Beta-2 agonists, long-acting: These drugs work the same way as
the short-acting beta-2 agonists, and are often used together with a
corticosteroid to provide long-term control. Used alone, they have minimal
anti-inflammatory activity. The long-acting beta-2 agonists start working
in 3 to 30 minutes and last for up to 8-12 hours after a single dose.
Side effects: Common side effects of long-acting beta-2 agonists
include restlessness, anxiety, sleeplessness, shakiness (tremors), and
headache. Different drugs have slightly different sets of side effects.
Cautions: Do not take more than the prescribed amount of long
acting beta-2-agonists. These agents are not designed for "as needed"
use and over-use could result in an over-dose. A safety study of the
drug Serevent (salmeterol xinafoate) involving about 26,000 subjects
found that the drug may be associated with a very slight increase in
serious asthma episodes and deaths, particularly in African Americans.
The increase was not statistically significant, and the Food and Drug
Administration strongly advises patients on the medication not to stop
taking it without talking to their doctors. Further investigation of
possible risks is planned. For more details on cautions and side effects
of asthma drugs, see the listing under short-term medicines, above,
and the entry in the table below.
Inhaled Corticosteroids: These are anti-inflammatory medications
that interfere in a broad way with the immune system and are used to
control many types of inflammation, which is simply the immune system's
response to an irritation or invader. In asthma treatment, corticosteroids
reduce the immune system's response to triggers in the airways and prevent
the resulting inflammation. That accounts for the reduction in inflammation
symptoms, such as airway hypersensitivity, swelling inside the airway
muscles, and mucus and secretions in the lungs.
Side effects:
Inhalers: Corticosteroids come in inhalers and pills. Common
side effects of the inhaled form include dry mouth, throat irritation,
hoarseness, rash, and thrush (yeast infection in the mouth). They can
be used in short bursts, in oral form to get symptoms under control
after an attack, or as long-term prevention (usually in the inhaled
form, but sometimes oral as well in severe asthma) for people with persistent
asthma.
Pills: The most common side effect of short-term pill dosages
is an upset stomach, which can lead to or aggravate a stomach ulcer.
Other common ones include change in appetite, emotional lability, water
retention, muscle weakness, potassium loss (tiredness, weakness, muscle
cramps), slower wound healing, increased blood sugar, sweating, rash,
itchiness, headache, dizziness, and convulsions. Because corticosteroids
act by interfering with the immune system, it's easier to catch infections
while taking them and harder to recover from new or existing infections.
For the same reason, don't get any vaccines without consulting your
doctor first.
The effects of long-term use, especially on high doses of pills, can
include adrenal suppression, bone loss, cataracts, glaucoma, stomach
ulcers, thinned skin, hair loss, "moon face," menstrual irregularities,
and "steroid psychosis" - symptoms can include mood swings,
sleeplessness, personality changes, and depression. There are many other
side effects from long-term use, so if you notice any unusual symptoms
please ask your doctor about them. If you're on long-term corticosteroid
treatment, it's very important for your current dosage to be tapered
down slowly (even if you're switching to a different form of the medicine)
to avoid serious complications such as adrenal insufficiency.
Cautions: Oral corticosteroids should be used with caution in
some people, including anyone who's had a recent heart attack and people
with osteoporosis, antibiotic-resistant infections (viral and fungal
especially), and cancer.
Interactions: Many drugs, including oral contraceptives, can
either increase or decrease the effects (and side effects) of corticosteroids,
so it's especially important to tell your doctor about all the drugs
you're taking, including over-the-counter medicines, and herbs. Corticosteroids
may also affect some lab tests.
Mast cells stabilizers: Mast cells are a type of immune cell
that carry different chemicals, including histamines, which mediate
and aggravate allergic responses. Mast cells tend to spill their contents
when there's trouble, and mast cell stabilizers keep that from happening.
They're also useful in preventing exercise-induced asthma.
Side effects and cautions: Side effects are uncommon. Skin rash
and itching are the most common side effects from the inhaled mast cell
stabilizers. Sometimes people experience a dry cough, throat irritation,
hives, or nausea after inhaling it. In rare cases,
it may cause a severe allergic reaction.
Interactions: This medication has no known drug interactions.
Leukotriene modifiers: Leukotrienes are one type of chemical
released by mast calls and other immune cells, and they cause airways
to constrict. They also stimulate mucus secretion and fluid buildup,
making the airways even narrower. Leukotriene modifiers are
designed to prevent leukotrienes from wreaking their havoc.
Side effects and cautions:
Leukotriene receptor antagonists: The most common side effect
of these drugs is headaches, and other common side effects include nausea,
diarrhea, and infections. Aspirin increases the amount of the drug in
the bloodstream, while theophylline and certain antibiotics can decrease
its effect. People with liver damage may need a lower dose.
Lipoxygenase inhibitors: The most common side effect is headache,
followed by general pain, nausea, upset stomach, and liver inflammation.
Zileuton can cause lowered white blood cell counts. People with active
liver disease should avoid it altogether, and if you're taking it, you'll
need periodic blood tests to check your liver function and blood counts.
Interactions: Both types of leukotriene modifiers enhance the
blood levels of many other drugs, so be sure to tell your doctor of
all the medications you're on.
Methylxanthines (Xanthine bronchodilators): This class of drugs
includes theophylline, a stimulant similar to caffeine but far more
powerful. Theophylline relaxes the muscles around the airways, but we
don't know exactly how. Because these drugs cause many side effects,
they're less often a first choice for longterm asthma control.
Theophylline and related drugs come in pill and syrup form. They're
also available as sustained or timed-release pills so you can take fewer
doses in a day. If you have this type of pill, it's important not to
chew or crush the pills, or take them with hot food or drinks, because
that will release too much of the drug too quickly into the body and
cause potentially dangerous side effects.
Side effects: The most common side effects are dose related and
occur mostly when blood levels are high. They include nausea, vomiting,
stomachache, diarrhea, restlessness, irritability, headache, trouble
sleeping, and faster heartbeat. These drugs can cause or worsen abnormal
heart rhythms.
Cautions: You should avoid methylxanthines if you have seizure
disorders, and use them with caution if you have a stomach ulcer, heart
disease, high blood pressure, or liver disease. If you're on a methylxanthine,
you'll need periodic blood tests to monitor your dosage and minimize
the side effects from these drugs.
Interactions: Caffeine is a methylxanthine too, so try to minimize
the amount of tea, coffee, chocolate, and caffeinated soft drinks you
have to keep your dosage within safe limits. Smoking decreases the effects
of methylxanthines. Many different drugs can interact with theophylline
and related drugs, either increasing or decreasing levels in the blood,
so it's especially important to tell your doctor about all the drugs
you're taking, including oral contraceptives, over-the-counter medicines,
and herbs. Methylxanthines themselves can interfere with other drugs,
including sedatives and anesthetics. People with thyroid disorders may
need their dose adjusted.
Anticholinergics: These drugs are sometimes used for long-term
control. For more information, see the listing under short-term medicines,
above, and the entry in Table 2.
Antihistamines: This type of allergy medicine works by blocking
histamine, which is released by mast cells. They fight itchiness, redness,
and swelling, but they may or may not help your asthma.
Decongestants: These drugs reduce congestion by constricting
the blood vessels in the nose, which decreases swelling, and mucus.
The most common decongestant is pseudoephedrine (found in Sudafed and
many other brand names). It's the synthetic form of ephedrine, the active
ingredient in the herb ephedra (known as ma huang in Chinese medicine).
Decongestants are stimulants, and the side effects of your other asthma
medications (bronchodilators) may be magnified if you take them.
Mucolytic agents: These drugs help dissolve excess mucous in
the airways, but it's unclear how useful they are in improving asthma
symptoms; they may also be irritating to the airway. Available drugs
include N-acetylcysteine (Mucomyst).
Further Resources
American Academy of Allergy, Asthma, and Immunology
800-822-ASMA http://www.aaaai.org
American College of Allergy, Asthma, and Immunology
800-842-7777 http://allergy.mcg.edu
American Lung Association
800-LUNG USA http://www.lungusa.org
Asthma and Allergy Foundation of America
800-7-ASTHMA http://www.aafa.org
References
The Pill Book, 9th edition (2000)
American Medical Association's Essential Guide to
Asthma (1998)
