Pharmacokinetics of azithromycin in patients with impaired hepatic function

The pharmacokinetics of azithromycin were determined over a 192-h period following oral administration of a single 500-mg dose to six healthy volunteers and to 16 cirrhotic patients (ten class A and six class B; Pugh's classification). Plasma and urinary levels were determined by microbiological assay. The mean Cmax, obtained 2-3 h after administration, was 0.29 mg/L in volunteers, and 0.39 and 0.51 mg/L in class A and class B cirrhosis, respectively. The elimination half-life was 53.5 h in control subjects, and 60.6 and 68.1 h in class A and class B cirrhotic patients, respectively. The mean residence time was significantly higher in class B patients, but AUC, Vd, Cltot and Clr values appeared to be similar in all groups. The mean urinary recovery of azithromycin at 192 h varied from 11-15.7%, and did not differ significantly among groups. These results demonstrate that azithromycin pharmacokinetics do not differ consistently in patients with mild or moderate hepatic impairment in comparison with healthy volunteers. Therefore, no dosage modifications of azithromycin seem to be required for patients with class A or B liver cirrhosis.