Age and Gender Effects on the Pharmacokinetics of Gatifloxacin

Study objective To compare the pharmacokinetics and safety of gatifloxacin in elderly (> or = 65 yrs) and young (18-45 yrs) men and women. Design Open-label, parallel-group, single-dose study. Setting GFI Pharmaceutical Services Inc., Evansville, Indiana, USA. Subjects Forty-eight healthy subjects in four groups of 12 each. Interventions Subjects received single oral doses of gatifloxacin 400 mg. Serial blood and urine samples were collected for 96 hours after dosing to determine drug concentrations. Measurements and main results Age and gender had moderate effects on the pharmacokinetics of gatifloxacin. Elderly women had a 21% higher geometric mean peak plasma concentration (Cmax) and a 32% higher area under the plasma concentration-time curve (AUC0-infinity) than young women. Adjustment for creatinine clearance had only a slight effect on Cmax but reduced the estimated effect of age on AUC0-infinity in women from a 32% increase to a 15% increase. Gender effects on pharmacokinetic values were noted among elderly subjects only. Geometric means for Cmax and AUC0-infinity were 21% and 33% higher, respectively, for elderly women and elderly men. Adjustment for body weight reduced these differences to 11% and 20%, respectively. Conclusion The effects of age on gatifloxacin pharmacokinetic values were largely attributed to declining renal function, whereas those of gender were largely attributed to differences in body weight. These modest age- and gender-related differences do not warrant dosage adjustment.