Physiological and neuropsychological effects of theophylline in chronic obstructive pulmonary disease.

The effect of oral theophylline on clinical course, exercise, neuropsychological performance and bronchial reactivity was studied in chronic airflow obstruction. Twelve patients with chronic obstructive pulmonary disease (COPD) [mean age 62.4 +/- 1.6 years (SE), and forced expiratory volume in 1 sec of 1.15 +/- 0.1 l] were randomized to 4 weeks treatment with oral theophylline followed by 4 weeks of placebo, in a double-blind fashion. During each period, patients underwent clinical evaluation, incremental exercise, a battery of neuropsychological tests measuring a wide range of cognitive functions, and an inhaled methacholine provocation. On the active drug (levels 9.5 +/- 1 mg/l), vital capacity and maximal breathing capacity were 16 +/- 7% and 20 +/- 7% respectively, higher relative to placebo (P < 0.04). Exercise capacity, as reflected by peak O2 uptake and the anaerobic threshold, improved 14 +/- 5% and 18 +/- 5% (P < 0.04). In contrast, bronchial responsiveness to inhaled methacholine and the mean scores on the neuropsychological tests were not significantly altered by the drug. Clinical symptoms were unaltered, but mild side effects were more common on theophylline. We concluded that in moderate to severe COPD, theophylline treatment, at the low range of the therapeutic dose, improves lung function and exercise capacity. This improvement is achieved with no detectable alteration of bronchial reactivity to methacholine and with no deleterious effect on cognitive functions.