What Everybody Ought to Know About Asthma

Asthma is the most common chronic disease among children. Asthma triggers include viral infections; environmental pollutants, such as tobacco smoke; certain medications, (aspirin, nonsteroidal anti-inflammatory drugs), and sustained exercise, particularly in cold environments.

Diagnosis

History

Symptoms of asthma may include episodic complaints of breathing difficulties, seasonal or nighttime cough, prolonged shortness of breath after a respiratory infection, or difficulty sustaining exercise.

Wheezing does not always represent asthma. Wheezing may persist for weeks after an acute bronchitis episode. Patients with chronic obstructive pulmonary disease may have a reversible component superimposed on their fixed obstruction. Etiologic clues include a personal history of allergic disease, such as rhinitis or atopic dermatitis, and a family history of allergic disease.

The frequency of daytime and nighttime symptoms, duration of exacerbations and asthma triggers should be assessed.

Physical examination. Hyperventilation, use of accessory muscles of respiration, audible wheezing, and a prolonged expiratory phase are common. Increased nasal secretions or congestion, polyps, and eczema may be present.

Measurement of lung function. An increase in the forced expiratory volume in one second (FEV₁) of 12 percent after treatment with an inhaled beta₂ agonist is sufficient to make the diagnosis of asthma. A similar change in peak expiratory flow rate (PEFR) measured on a peak flow meter is also diagnostic.

Treatment of asthma

Beta₂ agonists

Inhaled short-acting beta₂-adrenergic agonists are the most effective drugs available for treatment of acute bronchospasm and for prevention of exercise-induced asthma. Regular use of short-acting beta₂ agonists offers no advantage over “as needed” use. Levalbuterol, the R-isomer of racemic albuterol, offers no clinically significant advantage over racemic albuterol.

Salmeterol, a long-acting beta₂ agonist, has a relatively slow onset of action and a prolonged effect; it is not recommended for treatment of acute bronchospasm. Patients taking salmeterol regularly should use a short-acting beta₂ agonist PRN to control acute symptoms. Twice-daily inhalation of salmeterol has been effective for maintenance treatment in combination with inhaled corticosteroids and may be especially useful in patients with nocturnal symptoms.

Adverse Effects. Tachycardia, palpitations, tremor and paradoxical bronchospasm can occur, and high doses can cause hypokalemia.

Inhaled corticosteroids

Regular use of an inhaled corticosteroid can suppress inflammation, decrease bronchial hyperresponsiveness and decrease symptoms. Inhaled corticosteroids are recommended for treatment of patients with mild or moderate persistent asthma as well as those with severe disease.

Adverse effects. Recommended doses of inhaled corticosteroids are usually free of toxicity. Dose-dependent slowing of linear growth may occur within six to 12 weeks in some children. Decreased bone density, glaucoma and cataract formation have been reported. Churg-Strauss vasculitis has been reported rarely. Dysphonia and oral candidiasis can occur. The use of a spacer device and rinsing the mouth after inhalation decreases the incidence of candidiasis.

Leukotriene modifiers

Leukotrienes increase migration of eosinophils, production of mucus and edema of the airway wall, and cause bronchoconstriction. Montelukast and zafirlukast are leukotriene receptor antagonists. Zileuton inhibits synthesis of leukotrienes.

Montelukast ( Singulair) is modestly effective for maintenance treatment of intermittent or persistent asthma. It is taken once daily in the evening. As monotherapy it is less effective than inhaled corticosteroids, but addition of montelukast may permit a reduction in corticosteroid dosage. Montelukast added to oral or inhaled corticosteroids can improve symptoms.

Zafirlukast ( Accolate) is modestly effective for maintenance treatment of mild-to-moderate asthma It is less effective than inhaled corticosteroids. Taking zafirlukast with food markedly decreases its bioavailability. Theophylline given concurrently can decrease its effect. Zafirlukast increases serum concentrations of oral anticoagulants and may cause bleeding. Infrequent adverse effects include mild headache, gastrointestinal disturbances and increased serum aminotransferase activity. Drug-induced lupus and Churg-Strauss vasculitis have been reported.

Zileuton ( Zyflo) is modestly effective for maintenance treatment, but it is taken four times a day and patients must be monitored for hepatic toxicity.

Cromolyn ( Intal) and Nedocromil ( Tilade)

Cromolyn sodium, an inhibitor of mast cell degranulation, can decrease airway hyperresponsiveness in some patients with asthma. The drug has no bronchodilating activity and is useful only for prophylaxis. Cromolyn has virtually no systemic toxicity.

Nedocromil has similar effects. Both cromolyn and nedocromil are much less effective than inhaled corticosteroids.

Theophylline

Oral theophylline has a slower onset of action than inhaled beta₂ agonists and has limited usefulness for treatment of acute symptoms. It can, however, reduce the frequency and severity of symptoms, especially in nocturnal asthma, and can decrease inhaled corticosteroid requirements.

When theophylline is used alone, serum concentrations between 5 and 15 :g/mL are most likely to produce therapeutic results with minimal adverse effects.

Oral Corticosteroids are the most effective drugs available for acute exacerbations of asthma unresponsive to bronchodilators.

Oral corticosteroids decrease symptoms and may prevent an early relapse. Chronic daily use of oral corticosteroids can cause glucose intolerance, weight gain, increased blood pressure, bone demineralization leading to osteoporosis, cataracts, immunosuppression and decreased growth in children. Alternate-day use of corticosteroids can decrease the incidence of adverse effects, but not of osteoporosis.

Prednisone, prednisolone or methylprednisolone ( Solu-Medrol), 40 to 60 mg qd; for children, 1 to 2 mg/kg/day to a maximum of 60 mg/day. Therapy is continued for 3-10 days. The oral steroid dosage does not have to be tapered after short-course “burst” therapy if the patient is receiving inhaled steroid therapy.

Choice of Drugs

Both children and adults with infrequent mild symptoms of asthma may require only intermittent use, as needed, of a short-acting inhaled beta₂-adrenergic agonist. Overuse of inhaled short-acting beta₂ agonists or more than twice a week indicates that an inhaled corticosteroid should be added to the treatment regimen.

Management of acute exacerbations

High-dose, short-acting beta₂ agonists delivered by a metered-dose inhaler with a volume spacer or via a nebulizer remain the mainstays of urgent treatment.

Most patients require therapy with systemic corticosteroids to resolve symptoms and prevent relapse.

Hospitalization should be considered if the PEFR remains less than 70% of predicted. Patients with a PEFR less than 50% of predicted who exhibit an increasing pCO₂ level and declining mental status are candidates for intubation.

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