Development and Validation of a Sensitive and Specific Radioimmunoassay for the Determination of Cicaprost in Biological Samples

Abstract Cicaprost is a potent, chemically and metabolically stable PGI2-mimetic. Pharmacodynamic effects were observed after oral administration of ≍ 10 μg in man when plasma levels were in the low pg-range. The present report describes the development of a selective antiserum and a tracer with high specific activity and their use for the RIA determination of Cicaprost in biological samples. Cicaprost-[3H]-methylester with a specific activity of 819 GBq/mmol was used as a tracer. RIA-analyses were carried out with 0.05–0.5 ml plasma adjusted to pH 2 with 1 N HC1 and extracted with 2.5 ml diethylether. Separation of antiserum bound and unbound Cicaprost was achieved by the charcoal method. Extraction recovery of Cicaprost was ≍ 90 % at pH ≍ 2. The detection limit of the assay was 10–20 pg/ml plasma. Coefficients of variations were 6, 3 and 9 % (within-day, n = 5) and 25, 12 and 10 % (day-to-day, n = 11) at 50, 100 and 200 pg/ml. HPLC-chromatograms of plasma extracts did not reveal any peak apart from Cica...