How long does azithromycin take to work?

I was at my Dr. yesterday and was advised that a 5 day pack of Azithromycin stays in your body for 10 days total. So after you take your 5th pill (assuming that you are on the 5 day pack), you have 5 more days of the drug working in your system. She said it has a delayed release effect and that is why it is still effective 5 days after the last dose.