Individual theophylline dosing based on bioelectrical impedance analysis.

The role of bioelectrical impedance (BI) analysis in determining slow-release theophylline dosage was evaluated in fifteen healthy subjects given a standard 200 mg dose. Reactance and l/resistance were identified as the most significant predictors of pre-dose, steady-state theophylline concentrations (Css,pre). Compared with doses based on body weight (8.8 mg kg-1 day-1), theophylline doses determined by BI analysis (9.6 +/- 2.4 mg kg-1 day-1) resulted in less biased (mean prediction error = 0.6 vs 1.4) though slightly less precise (mean squared error = 7.1 vs 6.3) Css,pre values. These differences were statistically insignificant (P > 0.05).