title: Utility of capillary microsampling for rat pharmacokinetic studies: Comparison of tail-vein bleed to jugular vein cannula sampling.
abstract: BACKGROUND
  Serial sampling methods have been used for rat pharmacokinetic (PK) studies for over 20 years. Currently, it is still common to take 200-250 μL of blood at each timepoint when performing a PK study in rats and using serial sampling. While several techniques have been employed for collecting blood samples from rats, there is only limited published data to compare these methods. Recently, microsampling (≤ 50 μL) techniques have been reported as an alternative process for collecting blood samples from rats.
  
  
  METHODS
  In this report, five compounds were dosed orally into rats. For three proprietary compounds, jugular vein cannula (JVC) sampling was used to collect whole blood and plasma samples and capillary microsampling (CMS) was used to collect blood samples from the tail vein of the same animal. For the two other compounds, marketed drugs fluoxetine and glipizide, JVC sampling was used to collect both whole blood and blood CMS samples while tail-vein sampling from the same rats was also used to collect both whole blood and blood CMS samples.
  
  
  RESULTS
  For the three proprietary compounds, the blood AUC as well as the blood concentration-time profile that were obtained from the tail vein were different from those obtained via JVC sampling. For fluoxetine, the blood total exposure (AUC) was not statistically different when comparing tail-vein sampling to JVC sampling, however the blood concentration-time profile that was obtained from the tail vein was different than the one obtained from JVC sampling. For glipizide, the blood AUC and concentration-time profile were not statistically different when comparing the tail-vein sampling to the JVC sampling. For both fluoxetine and glipizide, the blood concentration profiles obtained from CMS were equivalent to the blood concentration profiles obtained from the standard whole blood sampling, collected at the same sampling site.
  
  
  CONCLUSIONS
  The data in this report provide strong evidence that blood CMS is a valuable small volume blood sampling approach for rats and that it provides results for test compound concentrations that are equivalent to those obtained from traditional whole blood sampling. The data also suggest that for some compounds, the concentration-time profile that is obtained for a test compound based on sampling from a rat tail vein may be different from that obtained from rat JVC sampling. In some cases, this shift in the concentration-time profile will result in different PK parameters for the test compound. Based on these observations, it is recommended that a consistent blood sampling method should be used for serial microsampling in discovery rat PK studies when testing multiple new chemical entities. If the rat tail vein sampling method is selected for PK screening, then conducting a bridging study on the lead compound is recommended to confirm that the rat PK obtained from JVC sampling is comparable to the tail-vein sampling.
authors.affiliation: Drug Metabolism and Pharmacokinetics, Sanofi, Waltham, MA, USA. Electronic address: walter.korfmacher@genzyme.com.
authors.forename: Walter
authors.initials: W
authors.lastname: Korfmacher
authors.affiliation: Drug Metabolism and Pharmacokinetics, Sanofi, Waltham, MA, USA.
authors.forename: Yongyi
authors.initials: Y
authors.lastname: Luo
authors.affiliation: Drug Metabolism and Pharmacokinetics, Sanofi, Waltham, MA, USA.
authors.forename: Stacy
authors.initials: S
authors.lastname: Ho
authors.affiliation: Drug Metabolism and Pharmacokinetics, Sanofi, Waltham, MA, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Sun
authors.affiliation: Drug Metabolism and Pharmacokinetics, Sanofi, Waltham, MA, USA.
authors.forename: Liduo
authors.initials: L
authors.lastname: Shen
authors.affiliation: Drug Metabolism and Pharmacokinetics, Sanofi, Waltham, MA, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Wang
authors.affiliation: Drug Metabolism and Pharmacokinetics, Sanofi, Waltham, MA, USA.
authors.forename: Zhongtao
authors.initials: Z
authors.lastname: Wu
authors.affiliation: Drug Metabolism and Pharmacokinetics, Sanofi, Waltham, MA, USA.
authors.forename: Yang
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Agilux, Worcester, MA, USA.
authors.forename: Gregory
authors.initials: G
authors.lastname: Snow
authors.affiliation: Drug Metabolism and Pharmacokinetics, Sanofi, Waltham, MA, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: O'Shea
mesh_terms: D000284:Administration, Oral; D000818:Animals; D019540:Area Under Curve; D001800:Blood Specimen Collection / Q000379:methods*; D002196:Capillaries; D002406:Catheterization, Peripheral / Q000379:methods*; D005473:Fluoxetine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000097:blood / Q000493:pharmacokinetics; D005913:Glipizide / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics; D006207:Half-Life; D007275:Injections, Intravenous; D007601:Jugular Veins; D008297:Male; D055616:Microtechnology / Q000379:methods*; D004364:Pharmaceutical Preparations / Q000008:administration & dosage / Q000097:blood*; D017207:Rats, Sprague-Dawley; D013623:Tail / Q000098:blood supply*
chemical_list: D004364:Pharmaceutical Preparations; D005473:Fluoxetine; C036139:norfluoxetine; D005913:Glipizide
keywords: Blood sampling methods; Cannula-bleeding; Capillary microsampling; Fluoxetine; Glipizide; Rat pharmacokinetic studies; Sampling site; Serial sampling in rats; Tail-bleeding