Evaluation of the Chiou method for determining theophylline dosages

The Chiou method for predicting maintenance dosages of theophylline using individual patient data was evaluated. Eighty patients receiving continuous infusions of aminophylline were studied. Each patient's theophylline clearance was predicted using two serum theophylline concentrations obtained at least six hours apart after starting the aminophylline infusion. This clearance value was then used to calculate a new infusion rate designed to achieve a target steady-state serum theophylline concentration. A follow-up concentration was obtained at steady state and used to determine a steady-state theophylline clearance for each patient. The mean predicted and calculated theophylline clearance and the mean predicted and measured serum theophylline concentration for the study population were very similar. Mean prediction errors for theophylline clearance and serum theophylline concentrations were not significantly different among any of the five subgroups of patients with factors that influence theophylline disposition. The Chiou method, using relatively few serum samples, provides a rapid and accurate means of individualizing aminophylline infusion requirements for patients with a wide range of theophylline disposition characteristics.