Theophylline kinetics in chronic obstructive airway disease in the elderly.

Theophylline kinetic studies, serial spirometric function tests, and arterial blood gas determinations were performed in 39 adult men with stable chronic obstructive airway disease (COPD). Subjects were given an intravenous aminophylline loading dose of 5.6 mg/kg and a maintenance dose of 0.9 mg/kg/hr for 6 hours. Elderly (greater than 60 years old) nonsmoking subjects had 36% lower theophylline clearance (Cl) and a 40% longer serum theophylline elimination t1/2 than did middle-aged (less than 60 years old) nonsmoking subjects (mean +/- SE; clearances of 32.6 +/- 3.2 [n = 13] and 50.7 +/- 8.5 ml/kg/hr [n = 8] and t1/2s of 11.0 +/- 0.8 and 7.4 +/- 0.8 hours, respectively). There were also differences in Cl and t1/2 between elderly and middle-aged subjects in both the smoking and nonsmoking groups: elderly group, Cl = 43.6 +/- 3.7 mg/kg/hr and t1/2 = 9.0 +/- 0.7 hours; middle-aged group, Cl = 57.6 +/- 6.0 mg/kg/hr and t1/2 = 6.7 +/- 0.6 hours). There was consistent improvement in spirometric functions in both nonsmoking and smoking elderly subjects: percent changes in forced expiratory volume in 1 second of 19% to 25%; in forced vital capacity of 25% to 31%; in forced expiratory flow at 25% to 75% of vital capacity of 59% to 67%; and in maximum mid-flow time of -25% to -30%, at serum theophylline concentrations of 10 to 13 mg/L (group mean). We conclude that elderly nonsmoking subjects with COPD cleared theophylline more slowly than did middle-aged, nonsmoking subjects with COPD.(ABSTRACT TRUNCATED AT 250 WORDS)