A modified fluorescence polarization immunoassay method incorporating fat emulsion (FE-FPIA) to determine cyclosporin a concentrations in rat skin

Yuji Kurosaki, Tomoya Asada, Nanae Yasumoto, Toshiaki Nakamura, Mikio Masada, Hiromu Kawasaki

Research output: Contribution to journalArticle

1 Citation (Scopus)


We have developed a simple, sensitive and reliable assay procedure for cyclosporin A (CyA), a modifed fluorescence polarization immunoassay method incorporating fat emulsion (FE-FPIA), to determine the CyA content in rat skin. The conventional fluorescence polarization immunoassay (FPIA) method for CyA using a commercially available FPIA kit, TDX® cyclosporine monoclonal whole blood, was modified. A fat emulsion for intravenous infusion, Intralipos®, was incorporated for dissolving the CyA extracted from the skin tissue, and a mixture of MeOH/purified water was used as the sample pretreatment medium instead of the precipitation reagent in the conventional FPIA kit intended for whole blood samples. These modifications enabled us to produce a reliable and the sensitive assay of CyA in skin tissue. The reproducibility (coefficient of variation), detection limit, and assay time for FE-FPIA were below 2%, 25 ng/ml, and about 24 min/24 samples, respectively, and were comparable with those for the whole blood samples determined by the conventional FPIA. Pre-purification of samples required by the HPLC assay is not needed in the FE-FPIA method. The usefulness of the FE- FPIA method in evaluating the topical pharmacokinetics of CyA in skin is discussed.

Original languageEnglish
Pages (from-to)539-542
Number of pages4
JournalBiological and Pharmaceutical Bulletin
Issue number5
Publication statusPublished - May 1999



  • Cyclosporin A
  • Fat emulsion
  • Fluorescence polarization immunoassay
  • Topical pharmacokinetics

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology, Toxicology and Pharmaceutics(all)

Cite this