Steady‐State Pharmacokinetics of Theophylline in COPD Patients Treated With Dirithromycin

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Abstract
Steady‐state theophylline pharmacokinetic parameters were studied in a panel of 14 patients with chronic obstructive pulmonary disease (COPD). Pharmacokinetic parameters were evaluated before, during, and after a 10‐day regimen of the macrolide antibiotic, dirithromycin. The addition of dirithromycin (500 mg orally once daily at 7:00 am) to a sustained‐release theophylline dosing regimen (every 12 hours) elicited small changes in the steady‐state pharmacokinetics of theophylline, which were not statistically significant. Mean steady‐state plasma theophylline trough concentrations (Css,min) were invariant before, during, and after dirithromycin treatment. Mean average steady‐state plasma theophylline concentrations (Cav) declined by 7% during dirithromycin treatment (NS), and mean peak plasma concentrations (Css,max) declined by 12% (NS). Theophylline clearance (CL/F) also remained relatively unchanged during dirithromycin treatment exhibiting an increase of only 11% (NS). Dirithromycin treatment does not significantly affect the steady‐state pharmacokinetics of theophylline, and its use in COPD patients is not likely to modify treatment outcomes with theophylline.