Concurrent use w/ CYP3A4 or P-gp inhibitors (eg, macrolides (clarithromycin & erythromycin), ciclosporin, ketoconazole, itraconazole, voriconazole, HIV PIs, Ca-channel blockers (verapamil, diltiazem) & disulfiram. Possibility of elevated serum colchicine conc w/ azithromycin. Contraindicated in patients w/ renal or hepatic impairment who are taking a P-gp inhibitor (eg, ciclosporin, verapamil or quinidine) or a strong CYP3A4 inhibitor (eg, ritonavir, atazanavir, indinavir, clarithromycin, telithromycin, itraconazole or ketoconazole).