Single and multiple dose pharmacokinetics of oral ciprofloxacin in elderly patients

The pharmacokinetics of oral ciprofloxacin were evaluated in 20 elderly patients with serious respiratory tract or musculoskeletal infections after single and multiple dose regimens of 750 mg of drug every 12 h. The single dose phase evaluations were performed on day 1 of therapy (n = 20) while the multiple dose phase evaluations were performed at the end of therapy (n = 11). Serum and urine ciprofloxacin concentrations were determined using high-performance liquid chromatography. Peak serum concentration (Cmax), terminal elimination half-life (t1/2 beta), apparent total body clearance (CL/f) and apparent volume of distribution (Vd/f) were 6.58 +/- 2.88 mg/l, 4.99 +/- 1.79 h, 6.69 +/- 3.73 ml/kg/min, and 2.87 +/- 1.86 l/kg, respectively, during the single dose phase. Only the Vd/f increased significantly during the multiple dose phase (4.40 +/- 3.32 vs. 2.71 +/- 1.53 l/kg, p = 0.047). Although Cmax increased and CL/f decreased markedly after multiple doses (8.83 +/- 2.79 vs. 6.65 +/- 2.28 mg/l, p = 0.057 and 5.61 +/- 2.53 vs. 6.53 +/- 3.03 ml/kg/min, p = 0.074, respectively), these changes were not statistically significant. The results of this study are consistent those previously derived from single dose studies in healthy and mildly-ill elderly subjects, but are markedly different from previous observations in young adult volunteers. Thus, acute illness does not significantly alter the pharmacokinetics of ciprofloxacin in the elderly suggesting that dosage adjustments based on the presence of acute illness do not appear warranted.(ABSTRACT TRUNCATED AT 250 WORDS)