Plasma digoxin concentrations in patients on admission to hospital.

Plasma digoxin concentrations on emergency admission to hospital were measured by radioimmunoassay in 10I patients who had been taking chronic maintenance digoxin therapy. The mean concentration was I4I nglml. Fifty-eight patients had plasma levels outside the range o-8 to 2-0 nglml: of these, 33 patients had levels below o-8 ng/ml and may not have been given sufficient digoxin, while 25 patients had levels greater than 2 0 nglml; 13 patients with a mean plasma digoxin concentration of 2 76 ngfml showed clinical evidence of digoxin toxicity. In the absence of clinical evidence of digoxin toxicity, it is impossible for the digoxin status of a patient who has been taking long-term treatment with the drug to be known without estimating his plasma digoxin concentration. The diffJculties of prescribing digoxin to such patients after admission to hospital are discussed.