The American Lung Association reports that 3,563 deaths in 2006 were asthma related. Asthma is a chronic condition that causes narrowing and inflammation of the airways. It is characterized by episodes of wheezing, coughing and shortness of breath. Asthma attacks can be triggered by allergies, exercise or illness, but people with severe asthma may experience some level of symptoms at all times. Proper management of the disease can reduce complications and give its sufferers a better quality of life.
Adrenoceptor Agonists
Adrenoceptor agonists, also referred to as sympathomimetic agents, relax the muscles that line the airway. They mimic the affect of adrenaline, the neurotransmitter your body releases in stressful situations to trigger the "fight or flight" response. Sympathomimetic agents are usually inhaled. This allows them to work directly on the lungs and lessens some of their side effects, such as rapid heart rate.
Epinephrine, ephedrine and isoproterenol are examples of sympathomimetic drugs, but they are rarely used due to the development of drugs that cause fewer side effects.
Albuterol, terbutaline, metaproterenol and pirbuterol are beta 2-selective adrenoceptor agonists. This means that they are most active on the lung tissues and less likely to cause side effects.
Salmeterol and formoterol are long-acting beta 2-selective agonists. These drugs remain effective for up to 12 hours after inhalation, but because they have been associated with sudden death, they are reserved for people whose asthma cannot be controlled with other medications.
Methylxanthine Drugs
Theophylline and caffeine are methylxanthine drugs. Their use has decreased with the development of inhaled therapies. The exact mechanism of action of methyxantine drugs is unknown, but it is likely that they inhibit enzymes known as phosphodiesterases. Two of the many functions of these enzymes is the relaxation the smooth muscle that lines the airway and the reduction of inflammation.
Antimuscarinic Agents
Antimuscarinic agents block the effect of the neurotransmitter acetylcholine. Acetylcholine causes the smooth muscle lining the airway to contract, which narrows the bronchial tubes. Antimuscarinic binds to and blocks the receptors that acetylcholine activates. Ipratropium bromide is an antimuscarinic drug.
Corticosteroids
Corticosteroids do not act directly on the smooth muscle lining the airway. Instead, they reduce the body's inflammatory response. They also lessen the sensitivity of the bronchial tubes to the triggers of asthmatic attacks. Corticosteroids can be taken orally or as an inhalation, but inhalation is prefereable due to the many side effects of corticosteroid drugs. Beclomethasone, budesonide, flunisolide, gluticasone, mometasone and triamcinoline are inhaled corticosteroid medications.
Mast Cell Stabilizers
Mast cells are one of the body's first responses to disease. In people with allergies, their bodies mistake the substance to which they are allergic for a disease-causing pathogen. Mast cell stabilizers inhibit mast cells and therefore reduce the allergic response. These drugs also appear to reduce some of the later responses to allergens. Cromolyn and nedocromil are mast cell stabilizers. They are given by inhalation.
Leukotriene Pathway Inhibitors
Leukotrienes are substances that trigger the body's response to inflammation. In asthma, leukotrienes cause sensitivity and constriction of the airway. They also increase in fluid and mucus in the bronchial tubes. The drug zileuton prevents the body from synthesizing leukotrienes, while the drugs sariflukast and montelukast block the action of leukotrienes in the lungs.
Anti-IgE Monoclonal Antibodies
For some people with asthma, their bodies release an antibody known as IgE when they are exposed to certain allergens. IgE then triggers the asthmatic response. The drug omalizumab captures IgE before an attack can begin. Omalizumab is reserved for people with severe asthma who have not been helped by other drugs. It is given by injection.
References
- American Lung Association: Trends in Asthma Morbidity and Mortality
- Basic and Clinical Pharmacology; Bertram Katzung; 2007
- Xolair Prescribing Information
