[Radioimmunological estimation of cardiac glycoside concentration in the plasma]

Radioimmunoassay is a simple method for estimating the concentration of cardiac glycosides in the blood. The technique is described. An condition of the accuracy of the estimation is that the drug levels in blood and tissue have reached equilibrium, since only then will the blood concentration accurately reflect the drug level in the tissues. The therapeutic plasma levels are 0.7 to 2.0 ng/ml for digoxin and 10-30 ng/ml for digitoxin. Indications for estimating the plasma glycoside levels are reviewed; they include suspected digitalis poisoning or intolerance, interaction of glycosides with other drugs and suspected negligence on the part of the patient to take the prescribed dose.