Effect of albumin on serum digoxin radioimmunoassays.

Clinical Chemistry (Impact Factor: 7.15). 04/1975; 21(3):402-6.
Source: PubMed

ABSTRACT The use of certain commerically available radioimmunoassay kits for measurement of digoxin results in errors in the determined digoxin concentration of patients when these kits are used according to manufacturers' directions. One factor that is, in part, responsible for these errors is a difference between standards and samples with respect to albumin concentration. Three of the four kits investigated showed a significant inverse relationship between the albumin concentration in the sample and the binding of radiolabeled digoxin by its antibody when the albumin concentration was varied over an extended range. It is apparent, however, that differences in albumin concentration do not completely explain the observed variations in the assay values.

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    ABSTRACT: Examining techniques for radioimmunoassay of digoxin in urine, we found that the apparent concentration of digoxin is affected by endogenous substances, independent of the concentration of digoxin itself. We describe a modification of the Becton Dickinson solid-phase RIA that makes it more nearly accurate and more easily performed, and obviates the endogenous interference. Digoxin concentrations from 5.0 to at least 1000 micrograms/L can be measured.
    Clinical Chemistry 02/1985; 31(1):122-4. · 7.15 Impact Factor
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    ABSTRACT: A study designed to investigate the relationship between the pharmacokinetics of digoxin and a measure of its pharmacological effect has been conducted. Serum digoxin concentrations and systolic time intervals were measured concurrently in 12 normal male volunteers following a 1.0 mg i.v. bolus injection. The averaged serum digoxin concentration--time and response--time data were analyzed pharmacokinetically using a three-compartment open model and nonlinear least-squares fitting. When only the serum level--time data were analyzed, a close relationship was found between calculated digoxin levels in the slowly distributing (deep) peripheral compartment and response of the heart to digoxin, as measured by changes in the QS2 index (delta QS2I). Although it was not possible to distinguish clearly a linear from a nonlinear relationship between digoxin levels in the deep compartment and delta QS2I, the nonlinear relationship gave the best overall fit when both serum digoxin and delta QS2I data were fitted simultaneously. The simultaneous fit yielded a total body clearance of digoxin of 3.6 ml/min/kg and a terminal t1/2 of 42 hr.
    Journal of Pharmacokinetics and Biopharmaceutics 03/1979; 7(1):47-61.
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