Theophylline pharmacokinetics in patients with mild or severe airway obstruction

A standard loading dose of aminophylline, followed by constant rate infusion for 3 h was used to study theophylline pharmacokinetics in 36 patients (age range 27-73 years) admitted to hospital during an exacerbation of chronic airway obstruction. The severity of the disease was assessed by peak expiratory flow rate and blood gas analysis. It was assumed that the severity of the disease and the patients' age, sex and smoking habits were relevant in predicting individual kinetics and hence in establishing individual theophylline dosage. Multiple regression analysis of the results failed to confirm this hypothesis and showed no significant relationship between the severity of the disease and pharmacokinetics even when other biological variables were taken into account. The results confirm the importance of careful monitoring of blood levels of theophylline since they cannot be predicted from functional indices of the severity of obstructive lung disease.