Preliminary Study of the Pharmacokinetics of Oral Amifloxacin in Elderly Subjects

Amifloxacin pharmacokinetics after a single oral dose in healthy elderly subjects were determined. Five males and five females aged 65 to 79 years and having creatinine clearances of 39.3 to 87.2 ml/h per kg of body weight were given a 200-mg amifloxacin caplet following an overnight fast. Mean (standard deviation) pharmacokinetic parameters for amifloxacin were as follows: maximum observed concentration in plasma, 1.13 (0.48) and 1.95 (0.52) micrograms/ml; half-life, 5.37 (0.96) and 4.47 (0.87) h; total plasma clearance (unadjusted for fraction absorbed), 259 (53) and 199 (55) ml/h per kg; renal clearance, 113 (20) and 86 (26) ml/h per kg; Varea/F (Varea is volume of distribution; F is fraction absorbed), 2.05 (0.75) and 1.28 (0.39) liter/kg; and amifloxacin excreted in the urine, 42.5% (14.5%) and 42.8% (10.6%) for males and females, respectively. There were no statistically significant differences in pharmacokinetic parameters between sexes that could not be attributed to differences in body weight. Except for a modest 23% reduction in renal clearance and the suggestion of reduced bioavailability, mean values of pharmacokinetic parameters for elderly male subjects were similar to those previously determined for younger male volunteers. Therefore, a modification in amifloxacin dosage regimen based solely on age may not be necessary.