Theophylline concentrations in patients with acute exacerbation of COPD

Patients with acute exacerbation of chronic obstructive pulmonary disease (COPD) frequently report a history of theophylline use prior to arrival in the emergency department. The reliability of using this history to guide aminophylline therapy is, however, unclear. The authors studied patients with an acute exacerbation of COPD to determine the relation between the initial theophylline level and the medication history. Seventy-nine patients with a mean age of 64.3 years were entered into the study. The average theophylline level was 10.8 micrograms/mL. Forty-seven percent of the patients had subtherapeutic levels, 46% had therapeutic levels, and 7% had toxic levels. There were weak although statistically significant correlations between the theophylline level and the interval since the last theophylline dose (r = -.40, P less than .001), as well as with the last recorded outpatient theophylline level (r = .45, P less than .001). However, the theophylline level could not be predicted accurately in a number of patients. The authors conclude, because the prediction rule was often inaccurate, aminophylline therapy in patients with acute exacerbation of COPD should be based on direct measurement of the serum theophylline level.