The pharmacokinetics and inflammatory fluid penetration of orally administered azithromycin

The pharmacokinetics of azithromycin were determined during a 24 h period following oral administration of a single 500-mg dose to each of six male volunteers. Concentrations in serum, urine and cantharides-induced inflammatory fluid were determined by microbiological assay. The mean peak serum concentration of 0.45 mg/l was obtained at a mean time of 2.6 h post-administration. The elimination half-life from serum was seen to increase with time post-dose; the mean elimination half-life at 16 h post-dose was 9.6 h. Inflammatory fluid was penetrated rapidly, with the mean peak concentration of 0.13 mg/l achieved at a mean time of 3.25 h post-dose. After this peak, levels initially decreased, but after 8 h from drug administration until the end of the trial period, inflammatory fluid concentrations remained relatively constant. The mean inflammatory fluid penetration up to the end of the study period was 74%. The mean urinary recovery of azithromycin, during the initial 24 h post-dose, was 6%.