Association Between CytochromeP4501A2 and CytochromeP4502E1 Gene Polymorphisms and Metabolism of Theophylline

Inclusion Criteria: * Aged 18-75 years,COPD patients, male or female; * regularly visiting our hospital; * taking a sustained-release preparation of theophylline continuously for at least 2 weeks Exclusion Criteria: * patients with renal or hepatic dysfunction; * patients with congestive heart failure; * patients with hypothyroidism or hyperthyroidism; * patients currently taking drugs likely to affect theophylline metabolism or who had taken such drugs in the preceding week; * patients with extreme obesity * patients with very severe Chronic Obstructive Pulmonary Disease(COPD)