Oral and intravenous pharmacokinetic profiles of doxofylline in patients with chronic bronchitis.

Serum doxofylline concentrations were evaluated after solid-phase extraction by high-performance liquid chromatography following administration of 100 mg doxofylline given as a single intravenous dose over 10 min or 400 mg doxofylline given orally twice daily for 5 days in six and eight non-smoking, fasting, chronic bronchitic patients, respectively. Doxofylline possessed a very short distribution phase following intravenous administration, with a sustained elimination phase (half-life 1.83 +/- 0.37 h). After oral administration, the peak serum doxofylline concentration was 15.21 +/- 1.73 micrograms/ml and the mean elimination half-life was 7.01 +/- 0.80 h; there was a large inter-subject variability. No side-effects were experienced by the patients during the study.