Bronchodilation from intravenous theophylline in patients with cystic fibrosis: results of a blinded placebo‐controlled crossover clinical trial

Most patients with cystic fibrosis (CF) eventually develop chronic obstructive pulmonary disease and theoretically could benefit from theophylline therapy. The purpose of this study was to investigate the pharmacologic response to intravenous theophylline by pulmonary function tests (PFT) and the theophylline pharmacokinetics in patients with CF. A randomized, double‐blind, placebo‐controlled, crossover trial was conducted in 10 ambulant patients with CF (5 females, 5 males), aged 11 to 21 years. Each patient received an intravenous dose of theophylline and normal saline over 1/2 hour on consecutive days. Spirometry and whole‐body plethysmography were performed at baseline, 1, 3, 5, and 7 h after the theophylline dose, and 10 blood samples were collected over 9 h on both study days. The percent change of PFT from the baseline was recorded. Analysis of variance for balanced two‐period crossover design was used to evaluate the effectiveness of theophylline therapy. The serum concentration (Conc.) vs. time data were fitted using nonlinear least‐squares regression analysis. The theophylline dose administered was 7.9 ± 0.4 (mean ± SD) mg/kg, which produced a maximal Conc. (C_max) of 14.6 ± 2.7 m̈g/ml. The half‐life (T_1/2), volume of distribution (Vd), and total body clearance (TBC) were 4.9 ± 1.9h, 537 ± 124 mL/kg, and 80 ± 16 ml/h/kg, respectively. The results of PFT data analysis indicated that maximal improvement in PFT was observed at 5 h, and statistically significant improvements occurred in forced expiratory flow during the first .75 s (FEV_.75), FEV_1.0, FEV_1.0/vital capacity (VC), FEF when 50% and when 75% of VC is expired, and FEF between 25% and 75% of VC (P <0.05). These results suggest that in CF patients, theophylline can produce a delayed but significant improvement in PFT.