Serum digoxin levels in patients of a general practice in Germany.

Serum digoxin levels were determined in 33 outpatients of a general practice in the countryside, on three occasions at intervals of 8 weeks. All the patients were on long term digoxin treatment, about 2 years on average. About 14 days after the first and the second visits the results of the measurements were sent to the patients, with a comment about their reliability in taking treatment according to the serum digoxin level. At the first visit half of the serum digoxin level were lower than 0.5 ng/ml; the mean serum concentration was 0.52 ng/ml. There was no correlation between serum concentration and age, dose or creatinine level; but there was with replies to the question about regularity of drug intake. The mean serum level at the second and the third visits was 0.88 ng/ml and 0.89 ng/ml, respectively. A correlation was found between the dose and the serum digoxin level. From these results it seems that compliance by the patient plays a major role in producing steady state levels of drugs.