lung and airway disorders
Drugs for Preventing and Treating Asthma
Beta Adrenergic Drugs
Short-acting beta-adrenergic drugs are usually the best drugs for relieving asthma attacks. They also are used to prevent exercise-induced asthma. These drugs are referred to as bronchodilators because they stimulate beta-adrenergic receptors to widen (dilate) the airways. Bronchodilators that act on all beta-adrenergic receptors throughout the body (such asepinephrine) cause side effects such as rapid heartbeat, restlessness, headache, and muscle tremors. Bronchodilators (such asalbuterol) that act mainly on beta-2-adrenergic receptors, which are found primarily on cells in the lungs, have less effect on other organs and thus cause fewer side effects. Most short-acting beta-adrenergic drugs, especially the inhaled ones, act within minutes, but the effects last only 2 to 6 hours. Quick medical attention should be sought when a person who has asthma feels the need to use more of a beta-adrenergic drug than is recommended. The need for extra use, particularly continuous use, indicates worsening bronchoconstriction, which can be dangerous, possibly risking even respiratory failure and death. Long-acting beta-adrenergic drugs are available, but they are used to prevent rather than to treat asthma attacks. Long-acting beta-adrenergic drugs are effective for about 12 hours, so people usually need two doses per day. The long-acting beta-adrenergic drugs are not used alone because people using only long-acting beta-adrenergic drugs may have a slightly higher risk of death. Thus, doctors always give them together with inhaled corticosteroids. Ultra–long-acting beta-adrenergic drugs are effective for up to 24 hours, so people need only one dose per day. Ultra–long-acting beta-adrenergic drugs are also not used alone because they may cause the same increase in the risk of death as long-acting drugs. Thus, doctors always give them together with inhaled corticosteroids. Metered-dose inhalers(handheld cartridges containing gas under pressure) are the most commonly used method for giving inhaled beta-adrenergic drugs. The pressure turns the drug into a fine spray containing a measured dose of drug. Inhalation deposits the drug directly in the airways, so that it acts quickly, but the drug may not reach airways that are severely narrowed. For people who have difficulty using a metered-dose inhaler, spacers or holding chambers can be used. These devices increase the amount of drug delivered to the lungs. With any type of inhaler, proper technique is vital. If the device is not used properly, the drug will not reach the airways. Adry powderdrug formulation is also available for many bronchodilators. The powder formulation is easier for some people to use, in part because it requires less coordination with breathing than when using a metered-dose inhaler. Shake the inhaler after removing the cap. Exhale fully for 1 or 2 seconds. Put the inhaler in your mouth or 1 to 2 inches from it and start to breathe in slowly, like sipping hot soup. While starting to breathe in, press the top of the inhaler. Breathe in slowly until your lungs are full. (This should take about 5 or 6 seconds.) Hold your breath for 10 seconds (or as long as you can). Breathe out and, if a second dose is required, repeat the procedure after 1 minute. If you find it difficult to coordinate breathing using this method, a spacer can be used. A nebulizercan be used to deliver beta-adrenergic drugs directly to the lungs. A nebulizer uses pressurized air or ultrasonic sound waves to create a continuous mist of drug that is inhaled without having to coordinate dosing with breathing. Nebulizers are often portable, and some units can even be plugged into a power outlet in a car. Nebulizers and metered-dose inhalers often deliver different amounts of drug with a single dose, but both are capable of delivering sufficient amounts of drug to the lungs. Nebulizer therapy is less likely to reach the more distant airways in people who are breathing comfortably and not taking deep breaths, making nebulized therapy less effective than a correctly used metered-dose inhaler or a dry powder formulation. Other bronchodilators, including the anticholinergic drugipratropiumdelivered through a nebulizer, may be combined with beta-adrenergic drugs for acute attacks. A combination ofipratropiumplusalbuterolgiven in a metered-dose inhaler is also available. of beta-adrenergic drugs are also available. Beta-adrenergic drugs can be taken in liquid or tablet form or injected. However, the oral drugs tend to work more slowly than the inhaled or injected ones and are more likely to cause side effects so doctors use them less often. Side effects include Overview of Abnormal Heart Rhythms , particularly with excessive use. 