title: Direct assessment of peripheral pharmacokinetics in humans: comparison between cantharides blister fluid sampling, in vivo microdialysis and saliva sampling.
abstract: OBJECTIVE
  Skin blister fluid sampling, in vivo microdialysis and saliva sampling are commonly employed as surrogates for the measurement of drug concentrations in peripheral compartments. Although expected to exhibit comparable results, data derived from these techniques have never been directly compared. Thus, the aim of the present study was to evaluate the comparability of these techniques.
  
  
  METHODS
  Paracetamol, a model drug with low protein binding, was administered to seven healthy volunteers at an oral dose of 2000 mg. Subsequently, tissue kinetics were measured simultaneously in cantharides induced skin blisters, microdialysates of subcutaneous- and skeletal muscle-tissue and saliva and compared to serum concentrations.
  
  
  RESULTS
  Mean ratio (AUCblister/AUCserum) was 0.88 (95% CI, 0.50-1.26), mean ratio (AUCmuscle/AUCserum) was 1.08 (0.67-1.49), mean ratio (AUCsubcutaneous/AUCserum) was 0.96 (0.41-1.51) and mean ratio (AUCsaliva/AUCserum) was 1.83 (1.39-2.27). In this study the concentration profiles after single oral administration differed among the three methods. The time course of the concentration (peripheral compartment)/concentration (serum)-ratios showed that cantharides blister and microdialysate concentrations closely paralleled serum levels. An equilibration period of less than 2 h had to be taken into account for blister measurements. In contrast, saliva concentrations were significantly higher than corresponding serum concentrations.
  
  
  CONCLUSIONS
  Skin blister sampling and microdialysis closely mirrored corresponding serum concentrations and, thus, proved to be suitable techniques for the assessment of peripheral compartment pharmacokinetics. In contrast, saliva data overestimated the corresponding serum concentrations.
authors.affiliation: Department of Clinical Pharmacology, University of Vienna Medical School, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Brunner
authors.forename: A
authors.initials: A
authors.lastname: Schmiedberger
authors.forename: R
authors.initials: R
authors.lastname: Schmid
authors.forename: D
authors.initials: D
authors.lastname: Jäger
authors.forename: E
authors.initials: E
authors.lastname: Piegler
authors.forename: H G
authors.initials: HG
authors.lastname: Eichler
authors.forename: M
authors.initials: M
authors.lastname: Müller
mesh_terms: D000082:Acetaminophen / Q000493:pharmacokinetics*; D000328:Adult; D019540:Area Under Curve; D001768:Blister / Q000139:chemically induced / Q000378:metabolism*; D002193:Cantharidin / Q000494:pharmacology; D015314:Dialysis Solutions / Q000737:chemistry; D005069:Evaluation Studies as Topic; D006801:Humans; D007509:Irritants / Q000494:pharmacology; D008297:Male; D017551:Microdialysis; D010599:Pharmacokinetics; D012463:Saliva / Q000737:chemistry / Q000378:metabolism*
chemical_list: D015314:Dialysis Solutions; D007509:Irritants; D000082:Acetaminophen; D002193:Cantharidin