An open study to compare the pharmacokinetics, safety and tolerability of a multiple-dose regimen of azithromycin in young and elderly volunteers

Abstract

An open, parallel study was conducted to compare the pharmacokinetics of oral azithromycin in young and elderly healthy volunteers. A total of 12 young subjects (six males, six females) with a mean age of 29 (range 22–39) years and another 12 elderly subjects (six males, six females) with a mean age of 72 (range 67–80) years were given a standard five-day therapeutic regimen of azithromycin (500 mg single dose on day 1 and 250 mg once daily on days 2–5). Pharmacokinetic results indicated that C_max, C_min and urinary excretion were similar in the two age groups. Mean AUC_0–24 was significantly greater (2.7 µg.h/ml) at day 5 in the elderly subjects compared with the younger age group (AUC_0–24=2.1 µg.h/ml) (p=0.041). Similarly, t_max values on days 1 and 5 were significantly greater in the elderly subjects; 3.8 h compared with 2.5 h in young subjects (p=0.005) on day 1 and 4.4 h, compared with 3.2 h (p=0.047) on day 5. There was also evidence of an inverse relationship between creatinine clearance and AUC_0–24 (p<0.01) but not urinary excretion or C_max. Despite these observations, it is concluded that the differences between the two age groups were of insufficient magnitude to warrant a dose modification in elderly subjects with only mild renal impairment. Side effects, chiefly headache and gastrointestinal symptoms, were reported by seven subjects in each group. No subject, however, was withdrawn from the study and there were no treatment-related abnormalities in any of the laboratory parameters measured.