A concurrent audit of high digoxin plasma levels.

A concurrent audit was made of 92 patients with plasma or serum digoxin levels of 3.0 ng/ml or more. Evidence of digoxin toxicity was present in 44 of these patients, and premature blood sampling accounted for the high levels in 30 nontoxic patients. Another 14 patients tolerated high digoxin levels without apparent adverse effects. Impaired renal function appeared to increase the risk of digoxin toxicity, even though digoxin levels were similar in patients with and without toxicity. Pharmacokinetic predictions based on patient weight and creatinine clearance often deviated considerably from measured digoxin levels even when these were drawn appropriately.