Twelve healthy volunteers were enrolled in an open-label, randomized, cross
over study. Subjects received single doses of theophylline (5 mg/kg) alone
and after a 10 day course of dirithromycin (two 250 mg tablets ed). The stu
dy phases were separated by a 3 week washout period. Serum samples were col
lected before and for 24 h after theophylline doses. Serum theophylline con
centrations were measured via a validated immunoassay system and the data w
ere modelled via non-compartmental analysis. When the control phase (i.e. n
o dirithromycin) was compared with the treatment phase (i.e. with dirithrom
ycin), theophylline exposures as measured by AUC(0->infinity) were not sign
ificantly different: 141.7 +/- 25.9 and 136.4 +/- 33.1 mg.h/L respectively
(P = 0.16). No significant changes in other theophylline pharmacokinetic pa
rameters were evident. These results indicate that theophylline can be safe
ly cc-administered with dirithromycin.