Concurrent administration of antacids containing aluminum or magnesium salts can reduce the rate, but not the extent, of absorption of azithromycin. Azithromycin and ergot derivatives should not be co-administered because of the theoretical possibilities of ergotism. Some of the macrolide antibiotics have been reported to impair the metabolism of digoxin (in the gut) in some patients. Increased rifabutin toxicity has been reported in patients receiving azithromycin and rifabutin.