After oral administration, Azithromycin is widely distributed throughout the body; bioavailability is approximately 37%. The time taken to reach peak plasma level is 2-3 hours. Plasma terminal elimination half-life closely reflects the tissue depletion half-life of 2 to 4 days. Kinetic studies have shown markedly higher Azithromycin levels in tissue than in plasma (up to 50 times the maximum observed concentration in plasma) indicating that the drug is highly tissue bound. Concentrations in target tissues such as lung, tonsil and prostate exceed the MIC 90 for likely pathogens after a single dose of 500mg.