Medical Health Encyclopedia

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. 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 beta2 agonists may reduce the effect of short-acting forms.

It's a major concern that patients who perceive beta2 agonists as being less effective may over-use them. Overdose can be serious and in rare cases even life-threatening, particularly in patients with heart disease.

Theophylline and Other Methylxanthines

Methylxanthines a number of actions in the lungs that should help COLD patients. They include opening airways, improving exchange of gases, reducing shortness of breath, improving mucus clearance, and stimulating the process of breathing. These agents are recommended by expert groups for patients with severe exacerbations or incomplete responses to bronchodilators.

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Unfortunately, a major 2003 analysis indicated these agents do not produce any significant improvement in lung functions, symptoms, or overall outcomes after treatment for acute exacerbations. Some experts, then, believe that these modest benefits do not outweigh the risk for the toxic effects commonly associated with these agents.

Nausea and vomiting occur in a third of patients, which can be serious side effects in COLD patients. Headache and insomnia are common. Cardiac arrhythmias and convulsions are possible. A physician should be contacted immediately if any of these side effects occur. Certain conditions (e.g., liver disease) and medications increase the risk for toxicity. Such medications include some antibiotics, calcium channels blockers, and H2 blockers such as famotidine (Pepcid AC), cimetidine (Tagamet HB), or ranitidine (Zantac 75).