The relationship between clearance of theophylline and age within the adult age range

Twenty volunteers aged between 20 and 57 years were given 197 mg of theophylline (as lysine theophylline) by iv infusion over 5 minutes to test the hypothesis that within the adult age range theophylline clearance declines with age. Samples were assayed for theophylline using the EMIT assay and clearance was determined by standard methods. Clearance values were 0.73 ml/min/kg below age 38 years and 0.75 ml/min/kg at and above age 38 years. Multiple regression analysis using age as a continuous variable showed no relationship between age and clearance.