Azithromycin × Theophylline

Azithromycin is a weak CYP1A2 inhibitor (theophylline is a substrate). Theophylline plasma levels may rise slightly. The effect is much smaller than with erythromycin or clarithromycin.

Mostly no changes. In patients with borderline theophylline levels: rare nausea, tachycardia, insomnia.

For short azithromycin courses (3–5 days), no special adjustment. In patients on high theophylline doses (or with renal/hepatic impairment): check theophylline level at 3–5 days.