A typical oral dose of Zithromax consists of 500 mg for 1 day then 250 mg for 4 days. A typical intravenous dose consists of 500 mg for 2 days followed by 500 mg orally daily for an additional 5-8 days. Aluminum- or magnesium- based antacids, such as Mylanta or Maalox will bind Zithromax and prevent its absorption from the intestine. Zithromax may increase the effect of Coumadin (warfarin). There are no adequate studies of Zithromax in pregnant women and it is not known whether Zithromax is excreted in breast milk. Only use Zithromax in pregnant or nursing mothers when absolutely necessary.