title: [Influence of CYP3A4/5 polymorphisms in the pharmacokinetics of levonorgestrel: a pilot study].
abstract: BACKGROUND
  Levonorgestrel a synthetic progestagen used for endometriosis, dysmenorrhea and emergency contraception, is quickly and completely absorbed in the digestive tract. levonorgestrel is predominantly metabolised through hepatic routes that utilise the CYP3A system (CYP3A4 and CYP3A5).
  
  
  OBJECTIVE
  This study aimed to evaluate the association between variant alleles of CYP3A4*1B and CYP3A5*3 polymorphisms and the pharmacokinetics of levonorgestrel.
  
  
  METHODS
  A group of 17 adult female healthy volunteers who signed an informed consent were genotyped for CYP3A4 and CYP3A5 through PCR-RFLP. Volunteers were submitted to pharmacokinetic analysis where, after a 12-hour overnight fast, they received a single oral dose of 0.75 mg of levonorgestrel. Serial blood samples were obtained (0 to 24 hours), and levonorgestrel concentrations were determined by UPLC-MS/MS to determine pharmacokinetic parameters. The procedures employed herein were performed according to the Declaration of Helsinki and Good Clinical Practices standards.
  
  
  RESULTS
  Observed genotype frequencies in the studied group for CYP3A4*1B were 11.8% for *1B/*1B, 5.8% for *1/*1B and 82.4% for *1/*1. CYP3A5*3 frequencies were 70.5% for *3/*3, 23.5% for *1/*3 and 6.5% for *1/*1. A high pharmacokinetic variability between volunteers was observed, but no statistical association of pharmacokinetic parameters was found within the studied CYP3A4/5 polymorphisms.
  
  
  CONCLUSIONS
  Genetic polymorphisms could be important factors in determining inter-patient variability in plasma levonorgestrel concentrations, which in this study were not significantly associated with the presence of CYP3A4*1B and CYP3A5*3 polymorphisms. Therefore, due to the significant inter-patient variability that we observed during the course of this study, it is necessary to carry out studies with larger number of volunteers.
authors.affiliation: Centro de Investigaciones Farmacológicas y Toxicológicas, Facultad de Medicina, Universidad de Chile, Santiago de Chile, Chile.
authors.forename: Iván
authors.initials: I
authors.lastname: Moreno
authors.forename: Luis
authors.initials: L
authors.lastname: Quiñones
authors.forename: Johanna
authors.initials: J
authors.lastname: Catalán
authors.forename: Carla
authors.initials: C
authors.lastname: Miranda
authors.forename: Ángela
authors.initials: Á
authors.lastname: Roco
authors.forename: Jaime
authors.initials: J
authors.lastname: Sasso
authors.forename: Evelyn
authors.initials: E
authors.lastname: Tamayo
authors.forename: Dante
authors.initials: D
authors.lastname: Cáceres
authors.forename: Andrei N
authors.initials: AN
authors.lastname: Tchernitchin
authors.forename: Leonardo
authors.initials: L
authors.lastname: Gaete
authors.forename: Iván
authors.initials: I
authors.lastname: Saavedra
mesh_terms: D000328:Adult; D000483:Alleles; D001711:Biotransformation / Q000235:genetics; D002677:Chile; D051544:Cytochrome P-450 CYP3A / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D016912:Levonorgestrel / Q000097:blood / Q000493:pharmacokinetics*; D010865:Pilot Projects; D011110:Polymorphism, Genetic; D020641:Polymorphism, Single Nucleotide; D011401:Promoter Regions, Genetic / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics; D055815:Young Adult
chemical_list: D020033:Protein Isoforms; D016912:Levonorgestrel; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human