Rationale for single and high dose treatment regimens with azithromycin.

The rationale for the use of single dose and shorter course azithromycin treatment regimens is based on the pharmacokinetic properties of azithromycin. The drug has a long elimination half-life (>50 h), which enables short course 1- or 3-day dose regimens to be clinically effective. Azithromycin is concentrated within phagocytic cells and tissues and it achieves targeted delivery by these cells to sites of infection. In vitro and in vivo models have demonstrated that azithromycin is taken up, transported and released at the sites of infection by phagocytic cells such as polymorphonuclear neutrophils and macrophages. Uptake is not saturable; therefore delivery of the total dose of azithromycin as a 1- or 3-day regimen should lead to increased uptake and delivery of the drug to sites of infection.