title: Effects of lanthanum carbonate on the absorption and oral bioavailability of ciprofloxacin.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
authors.affiliation: Department of Pharmacy Practice, College of Pharmacy, University of Illinois at Chicago, 833 S. Wood Street, Chicago, IL 60612, USA.
authors.forename: Priscilla P
authors.initials: PP
authors.lastname: How
authors.forename: James H
authors.initials: JH
authors.lastname: Fischer
authors.forename: Jose A
authors.initials: JA
authors.lastname: Arruda
authors.forename: Alan H
authors.initials: AH
authors.lastname: Lau
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000890:Anti-Infective Agents / Q000493:pharmacokinetics*; D019540:Area Under Curve; D001682:Biological Availability; D002939:Ciprofloxacin / Q000493:pharmacokinetics*; D018592:Cross-Over Studies; D004347:Drug Interactions; D005260:Female; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects*; D007811:Lanthanum / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D013997:Time Factors
chemical_list: D000890:Anti-Infective Agents; C119467:lanthanum carbonate; D002939:Ciprofloxacin; D007811:Lanthanum