Effects of Lanthanum Carbonate on the Absorption and Oral Bioavailability of Ciprofloxacin

BACKGROUND AND OBJECTIVES: Phosphate binders such as calcium salts or sevelamer, a cationic polymer, can markedly reduce absorption of oral ciprofloxacin. This randomized, open-label, two-way, crossover study examined the influence of the cation lanthanum on systemic ciprofloxacin exposure after oral administration. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Twelve patients randomly received in a crossover manner a single oral dose of ciprofloxacin 750 mg alone and plus lanthanum carbonate 1 g three times daily with meals for six doses, with a washout interval of 7 to 14 d. Serial blood and urine samples were collected for 24 h after ciprofloxacin administration, and ciprofloxacin concentrations were determined using reverse-phase HPLC. Pharmacokinetic parameters of ciprofloxacin were calculated by noncompartmental methods, and the effect of lanthanum on ciprofloxacin pharmacokinetic parameters was assessed using ANOVA. RESULTS: Lanthanum decreased (P < 0.001) the mean ciprofloxacin area under the plasma concentration-time curve by 54% and the maximum plasma concentration by 56%. The 24-h urinary recovery of ciprofloxacin was reduced by 52% by lanthanum (P < 0.001). No statistically significant differences in ciprofloxacin time to maximum plasma concentration, elimination half-life, and renal clearance occurred between the two arms. CONCLUSIONS: Lanthanum carbonate significantly reduces the systemic exposure to orally administered ciprofloxacin. Concomitant administration of both drugs should be avoided to prevent possible suboptimal response to ciprofloxacin.