Pharmacokinetics of ciprofloxacin in elderly subjects.

The pharmacokinetics of single-dose oral ciprofloxacin 500 mg was ascertained in 12 elderly and 12 young subjects. Mean age of the elderly volunteers was 75.4 years and the mean measured creatinine clearance in this group was 40.7 ml/min. Serum and saliva were collected in serial order for 24 hours (elderly) and 10 hours (young), and assayed for ciprofloxacin by high-performance liquid chromatography. The geriatric subjects had higher serum levels throughout the sampling period, with a peak level of 3.24 +/- 0.79 versus 2.26 +/- 0.75 micrograms/ml for the younger group (p less than 0.005; one-way analysis of variance). A twofold increase in the ciprofloxacin half-life may be partly explained by a decrease in the glomerular filtration rate, as shown by slower ciprofloxacin renal clearance (152.4 +/- 54.2 vs 395.6 +/- 139.0 for elderly and young subjects respectively; p less than 0.001). We concluded that in elderly patients, ciprofloxacin should be administered at an interval not less than every 12 hours to prevent accumulation and eventually toxicity.