title: High-performance liquid chromatographic analysis of cyclosporin A in rat blood and liver using a commercially available internal standard.
abstract: All the available HPLC assays of cyclosporin A (CyA) use internal standards that are not commercially available. Our purpose was to develop an HPLC assay for measurements of CyA in rat blood and liver using a commercially available internal standard (I.S.). After the addition of tamoxifen (I.S.), blood (0.25 ml) or the liver homogenate (1 ml) samples were extracted into a mixture of ether:methanol (95:5). The residue after evaporation of the organic layer was dissolved in 200 microl of an injection solution and washed with 1 ml of hexane before analysis. The separation was achieved using an LC-1 column (70 degrees C) with a mobile phase of methanol-acetonitrile-0.01 M KH(2)PO(4) (50:25:25, v/v) and a flow-rate of 1 ml/min. Detection was at 205 nm. Cyclosporin A and I.S. eluted at 5 and 7 min, respectively, free from endogenous peaks. Linear relationships (r>0.98) were observed between the CyA:I.S. peak area ratios and the CyA concentrations within the range of 0.2-10 microg/ml for blood and 0.1-4 microg/ml for the liver homogenates. The intra- and inter-run C.V.s and errors for both the blood and liver samples were <15%. The extraction efficiency (n=5) was close to 100% for both CyA and I.S. in both blood and liver homogenates. The lower limit of quantitation of the assay was 0.2 or 0.1 microg/ml based on 250 microl of blood or 1 ml of liver homogenate, respectively. The assay was capable of measuring blood and liver concentrations of CyA in a rat injected intravenously with a single 5-mg/kg dose of the drug.
authors.affiliation: School of Pharmacy, Texas Tech University Health Sciences Center, 1300 Coulter, Amarillo, TX 79106, USA.
authors.forename: Anjaneya P
authors.initials: AP
authors.lastname: Chimalakonda
authors.forename: Rakhi B
authors.initials: RB
authors.lastname: Shah
authors.forename: Reza
authors.initials: R
authors.lastname: Mehvar
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D016572:Cyclosporine / Q000032:analysis* / Q000097:blood; D008099:Liver / Q000737:chemistry*; D051381:Rats; D012015:Reference Standards; D015203:Reproducibility of Results
chemical_list: D016572:Cyclosporine