The pharmacokinetics of norfloxacin in the aged.

Eight patients aged over 65 years (mean age 81 years), with microbiologically proven urinary tract infections were treated with 400 mg norfloxacin bd daily for six days. Blood samples were taken on day 1 and day 6 to give a concentration-time profile, and on each of the other days samples were obtained before the first dose of the day. Urine was collected throughout. The mean of the maximum serum concentration of norfloxacin after the first dose was 1.5 mg/l (range 1.1-1.8 mg/l) at a mean of 3.2 h (range 1-6 h). After the last dose the mean maximum concentration was 2.2 mg/l (range 1.6-3.7 h) at 3 h (range 1-4 h). The mean serum half life was 5 h (range 3.7-6.5 h) on day 1 and 5.3 h range (4.4-6.2 h) on day 6. Serum pre-dose norfloxacin levels showed no evidence of accumulation. Mean urinary concentrations varied between 95 and 288 mg/l from day 1 to day 6. No significant adverse reactions were noted. No alteration of norfloxacin dose is suggested in the aged with normal renal function.