Management of Asthma and Chronic Airflow Limitation (Part 10)
Theophylline in Stable Chronic Airflow Limitation
The optimal maintenance bronchodilator treatment of COPD remains controversial. Inhaled bronchodilators and/or methylxanthines are widely used, either singly or in combination. Many patients with COPD have severe airflow limitation with symptoms of marked breathlessness and decreased exercise tolerance. Most physicians prescribe methylxanthines as first-line therapy, usually without attempting to quantify improvement objectively. Recent clinical trials suggest that the majority of patients with marked but relatively stable COPD derive little benefit from ingested theophylline therapy, either alone or when combined with inhaled adrenoceptor agonists. This contentious issue was reviewed extensively in a recent publication. buy prednisone
Recent studies have shown that small but statistically significant increases in mean FEV, and FVC occur in a subgroup of patients with severe COPD given theophylline if serum theophylline concentrations are maintained between 10 and 20 mg/L. On average, the FEV, increased by approximately 15 percent and the FVC by approximately 10 percent compared with placebo. There was, however, no demonstrable improvement in exercise tolerance or patient perception of breathlessness, raising questions about the clinical relevance of changes of this magnitude. For example, in one study theophylline did not improve exercise tolerance significantly compared with placebo during a 12-min walk test or during progressive cycle ergometry. Furthermore, in other studies, theophylline did not ameliorate symptoms of wheezing, breathlessness and cough or improve the patients* sense of well being.* It is likely that improvement of 10 to 15 percent in pulmonary function is simply too small to be appreciated by most patients, since it has been shown that the daily variability of FEV, in patients with stable COPD is at least 15 percent.