Ceftriaxone pharmacokinetics in elderly subjects and penetration into epididymis

In a prospective study, the epididymal penetration of ceftriaxone was evaluated in order to use it in the treatment of orchi-epididymitis in men. A bolus intravenous dose of 1 g of ceftriaxone was administered to 15 patients hospitalized for surgery as part of treatment for prostatic adenoma or prostatic cancer. Nine successive blood samples were collected in the interval from 0 to 24 h after administration, and epididymis samples were taken 0.75 h after administration. Concentrations of drug in all samples were assayed by a reverse-phase-ion pairing high-performance liquid chromatography method with UV detection. The results showed that the pharmacokinetics of ceftriaxone in serum did not differ from those determined previously in healthy volunteers. The terminal half-life was 6.9 +/- 1.7 h, and the mean residence time 9.5 +/- 2.3 h. The volume of distribution was 0.144 +/- 0.018 1 kg-1 and the total body clearance 1.17 +/- 0.29 l h-1. The concentrations in tissue reached 27.2 +/- 6 micrograms g-1 in righ epididymis, and 25.4 +/- 6.2 micrograms g-1 in left epididymis. The tissue-versus-serum concentration ratios ranged from 0.175 to 0.545 (mean value, 0.295 +/- 0.099). The concentrations in serum and tissue observed in this study were in excess of the MICs for bacteria considered to be susceptible to ceftriaxone, particularly Neisseria gonorrhoeae and coliform bacteria.