AZITHROMYCIN CLINICAL PHARMACOKINETICS

Azalide antibiotics, of which azithromycin is the first demonstrated, have different pharmacokinetics from other antibiotics currently used. The bioavailability of the drug is approximately 37%. Extensive and r apid distribution from serum into the intracellular compartments is fo llowed by rapid distribution to the tissues. Tissue concentrations exc eed serum concentrations by up to 100-fold following a single azithrom ycin 500mg dose. Concentration of the drug within phagocytes aids in i ts ability to combat infections. High concentrations of azithromycin a re found in the tonsil, lung, prostate, lymph nodes and liver, with on ly small concentrations found in fat and muscle. A 500mg dose on day 1 , followed by 250mg daily on days 2 to 5, has been demonstrated to mai ntain azithromycin concentrations at sites of infection and continues to be effective for several days after administration has ceased. The pharmacokinetics of azithromycin make it a drug with diverse therapeut ic applications.