Management of Asthma and Chronic Airflow Limitation (Part 11)
Two studies included in Hills review reported improved symptoms with theophylline treatment. However, there was no associated improvement in spirometry nor in exercise performance. Thus, although study patients experienced significantly less breathlessness, this was not reflected in greater functional capacity. Moreover, the small number of patients studied in both series limits the generalizability of the conclusions.
There is some evidence from two other studies that the simultaneous administration of both inhaled beta adrenergic bronchodilator and oral methylxanthine produces greater bronchodilatation than either drug alone. However, the additional benefit from a second bronchodilator was generally small and of uncertain clinical relevance. The major shortcoming of both trials is that doses of salbutamol used (200 \ig four times a day) were presumably suboptimal in many of these patients since much larger doses may be needed to achieve the plateau of the dose-response and no attempt was made to optimize the dose prior to the study. This suggests that if larger doses of salbutamol had been employed, the addition of theophylline may not have been beneficial.
In the two studies that assessed the benefit of adding dose-optimized theophylline to larger doses of albuterol (200 to 3,000 mg)* significant but modest additional improvement in pulmonary function was manifested in about 40 to 50 percent of the patients (responders), but the clinical relevance of this benefit was not addressed.