Direct micro-radioimmunoassay of the new renin inhibitor CGP 60536.

A solid phase method for direct radioimmunoassay in plasma of the new renin inhibitor CGP 60536 has been developed which does not require the extraction of the parent drug with organic solvents. The assay showed a good reproducibility down to plasma concentrations of 0.15 ng/ml (LOQ) with intra- and inter-assay coefficients of variation < or = 20%. The procedure, which requires only small volumes of plasma (25 microl), is simple to use and well suited for routine analysis. The method allows the investigation of the pharmacokinetics of CGP 60536 in animals and man given low oral doses of the drug.