Radioimmunoassay of the anti-hypertensive agent debrisoquin.

Antisera to debrisoquin, a widely used anti-hypertensive agent, have been obtained from rabbits following immunization with a conjugate of 4-[1,2,3,4-tetrahydroisoquinolin-2-yl)(imino)-methylamino] butanoic acid and bovine serum albumin. Employing tritium labelled debrisoquin as the radioligand for the antisera, a radioimmunoassay (RIA) was developed which allows for the specific determination of the drug directly in plasma. After logit transformation, a linear calibration line was obtained between 0.1 to 10 ng of unlabelled debrisoquin. The 4, 5, 6, 7 and 8-hydroxy derivatives of debrisoquion, known metabolites in man, showed less than 1.5% cross-reaction with the antisera. The specificity of the RIA was established when good agreement was obtained for the levels of debrisoquin in patients' plasma using the RIA and a specific GC/MS method. The simplicity of the RIA makes this method attractive for the routine clinical monitoring of the plasma levels and/or experimental protocols in which high sample throughput is required.