title: Ciprofloxacin bioavailability is enhanced by oral co-administration with phenazopyridine: a pharmacokinetic study in a Mexican population.
abstract: BACKGROUND
  and objective: In Mexico, urinary tract infections (UTIs) constitute the second most frequent type of infections treated at primary-care clinics. Ciprofloxacin has played a major role in the treatment of UTIs because it has a broad spectrum of antibacterial activity. In addition to antimicrobial agents, phenazopyridine has been used to alleviate symptoms that occur during episodes of UTI. Thus, the present study was designed to compare the pharmacokinetic behaviour of ciprofloxacin administered alone versus ciprofloxacin combined with phenazopyridine.
  
  
  METHODS
  Twenty-four healthy male Mexican volunteers participated in this project. The study was carried out with a single oral dose of ciprofloxacin 500mg. The double-blind, crossover, randomised, balanced trial design comprised two treatments, two periods and two sequences. After administration of the study medication, serial blood samples were collected for a period of 12 hours. The harvested plasma was analysed for ciprofloxacin by high-performance liquid chromatography. The area under the concentration-time curve to last measurable concentration (AUC(t)), area under the concentration-time curve extrapolated to infinity (AUC(infinity)), peak plasma concentration (C(max)), time to reach C(max) (t(max)), mean residence time (MRT), elimination constant (k(e)) and elimination half-life (t(1/2)) were determined from plasma concentrations of both treatments and considered as primary variables for statistical analysis.
  
  
  RESULTS
  While there were no differences between the two treatments in terms of C(max) and k(e), AUC(t )and AUC(infinity) were 35% and 29% higher, respectively, in the combined treatment arm. Moreover, a significant delay in t(max )(from 1 to 1.5 hours) and a statistical increase of 29% in MRT were also observed with phenazopyridine co-administration.
  
  
  CONCLUSIONS
  Oral co-administration of phenazopyridine increases ciprofloxacin bioavailability with regard to the amount absorbed (AUC) and permanence in the body (MRT), which could be useful during treatment.
authors.affiliation: Servicio de Investigación de Farmacología Clínica, Hospital General de México, Mexico City, Mexico. gabmaecelin@hotmail.com
authors.forename: Gabriel
authors.initials: G
authors.lastname: Marcelín-Jiménez
authors.forename: Alionka P
authors.initials: AP
authors.lastname: Angeles
authors.forename: Luis
authors.initials: L
authors.lastname: Martínez-Rossier
authors.forename: Adolfo
authors.initials: A
authors.lastname: Fernández S
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000779:Anesthetics, Local / Q000493:pharmacokinetics / Q000652:urine; D000890:Anti-Infective Agents / Q000097:blood / Q000493:pharmacokinetics / Q000652:urine; D019540:Area Under Curve; D001682:Biological Availability; D002851:Chromatography, High Pressure Liquid; D002939:Ciprofloxacin / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004338:Drug Combinations; D004347:Drug Interactions; D006207:Half-Life; D006801:Humans; D008297:Male; D008657:Metabolic Clearance Rate; D008800:Mexico; D009325:Nausea / Q000139:chemically induced; D010621:Phenazopyridine / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics*; D013607:Tablets; D013997:Time Factors
chemical_list: D000779:Anesthetics, Local; D000890:Anti-Infective Agents; D004338:Drug Combinations; D013607:Tablets; D002939:Ciprofloxacin; D010621:Phenazopyridine