INTRODUCTION

Our lungs contain many branching airways that deliver fresh air to the blood, as shown below.

Lungs and airways, from BREATHE EASY, by Lawrence Martin, MD. Top figure shows both lungs and the large branching airways. Airways divide into the bronchioles, which are the smallest airways before reaching the alveoli, where oxygen and carbon dioxide are exchanged between blood and the atmosphere. Inhaled asthma drugs work on the larger airways shown in the top figure, and not on the alveli.

The phrase "drugs for asthma and COPD" means drugs that help open up the airways when they become narrowed due to disease. COPD, or chronic obstructive pulmonary disease, includes "chronic bronchitis" and "emphysema," conditions which often co-exist in the same patient. Patients with COPD may also have asthma or an "asthma component." Also, patients originally diagnosed "with asthma" may have features of COPD. As a result of this overlap, the same drugs are commonly used in patients with any of the following diagnoses:

-- Asthma
-- COPD
-- Chronic bronchitis
-- Emphysema
-- Asthmatic bronchitis

Other drugs may be used in patients who suffer from asthma and COPD, such as antibiotics for infection, but they are not used to directly "open up" the airways.

When it comes to drugs for "opening up" the airways, all available medications can be classified by one of two basic mechanisms of action: bronchodilater and anti-inflammatory.

Bronchodilators "dilate" or open up the bronchi, which are the larger airways delivering air inside the lungs (see top figure). They do this by acting on smooth muscle in the walls of the bronchi. Anti-inflammatory drugs, by contrast, act to decrease the inflammation inside the airways; in this case "inflammation" means fluid and cellular debri that tends to clog up the airways of people with asthma and COPD.

Based on specific biochemical mechanism of action, there are 3 types of bronchodilators and 3 types of anti-inflammatory drugs used in asthma and COPD, This should be a simple classification, but complexity arises because within each of these 6 categories, the drugs can be given by different routes (e.g., orally with a pill; inhalation with a spray or dry powder; by injection into the tissues or directly into the vein) and similar drugs can be used for different purposes.

For example, while most bronchodilators are given by inhalation, and are used mainly for immediate relief of symptoms, several newer ones (such as Serevent, Foradil and Spiriva) are "long acting", and used mainly to prevent symptoms, not to provide immediate relief.

The situation with anti-inflammatory drugs is even more complicated. Steroids (also known as corticosteroids) are powerful anti-asthma drugs that work by reducing airway inflammation. However, they only provide relief of symptoms when taken in pill form or when injected into the muscle or directly into the vein. When steroids are inhaled, they don't provide sufficient dose to relieve symptoms; instead, the low dose of inhaled steroids is used mainly to prevent a worsening of symptoms, or to improve mild symptoms over the long term (days).

Another class of anti-inflammatory drugs, called mediator-release inhibitors (brand names Cromolyn and Tilade), also doesn't provide quick relief of symptoms; the two drugs in this group are used mainly as preventive medication, i.e., to prevent symptoms from worsening or from occurring in the first place.

The newest of the three classes of anti-inflammatory drugs are the anti-leukotrienes (brands are Accolate, Singulair, Zyflo). They also doesn't provide any quick relief, but may help to control asthma symptoms over the long term.

How is the patient to sort all this out?

Of the drugs listed below, only Primatene Mist (a short acting, inhaled bronchdilator) is sold over the counter in the U.S. All others are by prescription only. Primatene is a very short acting drug, and while it can provide some immediate relief, it does not provide any anti-inflammatory activity. Thus it is imperative that any suffering asthmatic or COPD patient get under the care of a physician who is knowledgeable about the available medications and how to manage flareups of asthma and COPD.

One other point needs to be made about COPD, or chronic obstructive pulmonary disease. COPD is found mainly in long term smokers. The term COPD comprises two similar conditions, chronic bronchitis and emphysema. It is usually not important to distinguish whether a person has mainly chronic bronchitis or emphysema; physicians routinely use "COPD" to cover either one or both conditions.

What is important is to recognize that symptoms of a flare up of COPD (e.g., cough, shortness of breath, wheezing, chest congestion) can be identical to symptoms from asthma, so the same drugs listed below are used in both conditions: asthma (which itself is not due to smoking) and COPD (usually due to smoking). There is very little, if any, difference in the use of these drugs in treating symptomatic COPD and asthma patients.