Beta2-agonists have serious interactions with certain other drugs, such as beta-blockers, and patients should tell the doctor about any other medications they are taking. Individuals with diabetes, existing heart disease, high blood pressure, hyperthyroidism, an enlarged prostate, or a history of seizures should take these drugs with caution.
Loss of Effectiveness and Overdose. There has been some concern that short-acting beta2-agonists become less effective when taken regularly over time, increasing the risk for overuse. Over time some patients may become tolerant to many effects of short-acting beta2-agonists. The degree to which this affects the airways is uncertain. In some studies, the duration of action has declined but the peak effect appears to be preserved, making these drugs still useful for acute attacks. Regular use of long-acting beta 2-agonists may reduce the effect of short-acting forms.
A 2005 landmark study suggested that patients’ differing clinical response to albuterol may be based on their genotype. Albuterol targets the beta-adrenergic receptor. In the Beta-Adrenergic Response by Genotype (BARGE) trial, researchers studied the effects of albuterol on patients with two different forms of this receptor. The results suggested that patients with the arginine form of the receptor did not respond to albuterol. These patients’ asthma symptoms actually improved when albuterol was not used. By contrast, patients with the glycine form of the receptor had improved asthma control with albuterol.
Patients who perceive beta2-agonists as being less effective may overuse them. Overdose can be serious and in rare cases even life-threatening, particularly in patients with heart disease.
Anticholinergic Drugs
Inhaled ipratropium bromide (Atrovent) acts as a bronchodilator over time. Ipratropium bromide alone is only modestly beneficial for acute asthma attacks. Moreover, the drug is not approved specifically for asthma. It may, however, have benefits in certain cases:
- It may be useful for certain older patients with asthma who also have emphysema or chronic bronchitis.
- A combination with a beta2-agonist might be helpful for patients who do not initially respond to treatment with a beta2-agonist alone.
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