Azithromycin: An assessment of its pharmacokinetics and therapeutic potential in CAPD

Background., Azithromycin is an azalide antibiotic with a similar antibacte rial spectrum to erythromycin but with greater gram-negative activity. Azit hromycin displays a favorable pharmacokinetic profile, with improved absorp tion and higher sustained tissue concentrations compared with erythromycin. This results in a prolonged elimination half-life, suggesting a potential for treating continuous ambulatory peritoneal dialysis (CAPD) peritonitis. Objective:This study aimed to define the potential role of azithromycin in treating CAPD peritonitis. Design:The pharmacokinetics and peritoneal dialysis (PD) clearance of azith romycin were studied following a single 500-mg oral dose of azithromycin. B lood and dialysate samples were taken over a 10-day period and assayed usin g high-pressure liquid chromatography. Setting: The study took place within the Renal Unit at Southend Hospital NH S Trust, a district general hospital in the United Kingdom. Patients: Eight patients with oliguric end-stage renal failure without peri tonitis maintained on CAPD (3 x 2 L/day). * Results: Peak plasma concentrations occurred at 2 3 hours with 0.35 - 1.35 mug/mL (mean 0.75). The mean elimination half-life was 84.55 hrs, and plasm a clearance was 21.93 L/hour. This compares with values of greater than 40 hours and 40.8 L/hour reported in healthy volunteers. After 8 hours, the me an dialysate concentration was 0.07 mug/mL; PD clearance was 0.06 L/hr. Conclusion: Azithromycin is not substantially removed by CAPD in the absenc e of peritonitis and cannot be recommended for widespread use in this setti ng at present. However, the successful use of azithromycin in CAPD peritoni tis, due possibly to an intracellular drug transport mechanism, has been re ported. Future research should address this possibility.