There have been reports of an interaction when theophylline and macrolides are given together, and also when carbamazepine is given with macrolides. We compared the kinetics of theophylline and carbamazepine, given alone and then in combination with roxithromycin. Roxithromycin had little effect on the pharmacokinetics of theophylline and none on carbamazepine, and roxithromycin can be given with either of the drugs without any need to alter the dose.