title: A radioimmunoassay method for the determination of nedocromil sodium in plasma and urine.
abstract: A radioimmunoassay method for the determination of nedocromil sodium (FPL 59002 disodium salt) in human plasma and urine is described. The method employs a primary antiserum raised in a sheep, and a mono-tyramide derivative of nedocromil sodium labelled with iodine-125 as a heterogeneous radioligand. Free and bound radioligand are separated using a secondary anti-sheep IgG antiserum. All three reagents are added simultaneously to samples containing nedocromil sodium prior to an overnight incubation. The method has a limit of detection of 0.25 ng ml(-1), when plasma sample volumes of 100 microl are analysed, and is accurate and precise. Inter-assay relative standard deviations (N = 18) of 15.1, 5.0 and 5.6% were found at concentrations in plasma of 0.5, 2.0 and 6.0 ng ml(-1) respectively. The method is specific as indicated by negligible cross-reaction of the anti-nedocromil sodium antiserum with a range of drugs. The method is applicable to the analysis of samples from subjects who have inhaled nedocromil sodium from a pressurised aerosol.
authors.affiliation: Fisons plc, Pharmaceutical Division, Research and Development Laboratories, Department of Metabolic Studies, Bakewell Road, Loughborough, Leicestershire, LE11 ORH, UK.
authors.forename: J J
authors.initials: JJ
authors.lastname: Gardner
authors.forename: J R
authors.initials: JR
authors.lastname: Preston
authors.forename: C M
authors.initials: CM
authors.lastname: Gilbert
authors.forename: D J
authors.initials: DJ
authors.lastname: Wilkinson
authors.forename: W J
authors.initials: WJ
authors.lastname: Lockley
authors.forename: K
authors.initials: K
authors.lastname: Brown