[Pharmacokinetics of ofloxacin in the elderly (65-85 years) with normal renal function after a single oral dose of 200 mg].

Ofloxacin is a fluoroquinolone that is mainly eliminated through the kidneys. We studied ofloxacin pharmacokinetics following administration of a single oral 200 mg dose to each of 16 elderly patients (77 +/- 2.4 years). Serum and urine concentrations were assayed using high performance liquid chromatography. Peak serum ofloxacin concentrations were 3.60 (+/- 0.36) micrograms/ml; residual concentrations were 1.33 (+/- 0.15) and 0.62 (+/- 0.10) micrograms/ml at 12 and 24 hours respectively. Urine concentrations approximating 100 micrograms/ml were found up to the 12th hour. As compared to healthy adults, in elderly subjects ofloxacin distribution volume (85.3 +/- 6.3 l) was decreased by 34%, apparent clearance (4.97 +/- 0.53 l/h) was divided by 2.6 and elimination half life (13.3 +/- 1.2 h) was almost doubled. A linear correlation was found between individual apparent ofloxacin clearances and creatinine clearances. In view of these significant changes in ofloxacin pharmacokinetics found in elderly subjects, we advocate reducing the usual dosage by half.