A CASE SERIES OF HOSPITALIZED-PATIENTS WITH ELEVATED DIGOXIN LEVELS

PURPOSE: Although there is renewed enthusiasm for the use of digoxin i n patients with heart failure, current dosing guidelines are based on a nomogram published in 1974. We studied the incidence of and risk fac tors for elevated digoxin levels in patients admitted to a community h ospital, and compared their dosage regimens to published guidelines. S UBJECTS AND METHODS: We reviewed the charts of all patients who had se rum digoxin levels greater than 2.4 ng/mL during a 6-month period. We collected demographic and clinical data, indications for digoxin use, digoxin dosage, concurrent medications, laboratory data, and clinical and electrocardiographic features of digoxin toxicity. RESULTS: Of the 1,433 patients with digoxin assays, 115 (8%) patients had elevated le vels. Of the 82 patients with complete records and correctly timed dig oxin levels, 59 (72%) had electrocardiographic or clinical features of digoxin toxicity. Patients with serum digoxin levels >2.4 ng/mL were slightly older (78 +/- 8 versus 73 +/- 9 years of age; P = 0.12) and h ad greater serum creatinine levels (3.1 +/- 7.3 versus 1.4 +/- 0.3 mg/ dL; P = 0.01) than those with levels less than or equal to 2.4 ng/mL. Forty-seven patients had elevated digoxin levels on admission, includi ng 21 patients admitted for digoxin toxicity. Impaired or worsening re nal function contributed to high levels in 37 patients, and a drug int eraction was a contributory factor in 10 cases. Twenty (43%) of these patients were taking the recommended maintenance dose based on the sch eme employed in the Digitalis Investigation Group study. Thirty-five p atients developed high digoxin levels while in hospital. In 26 patient s, this followed a loading dose of digoxin for the control of rapid at rial fibrillation. Impaired renal function was implicated in all of th ese patients. Despite the elevated digoxin level, rate control was ach ieved in only ii patients of these patients. CONCLUSIONS: Elevated dig oxin levels and clinical toxicity remains a common adverse drug reacti on. Elderly patients, particularly those with impaired renal function and low body weights, are at the greatest risk. As published digoxin n omograms often result in toxicity, clinical variables need to be monit ored. In patients with congestive heart failure and normal sinus rhyth m the potential benefit of digoxin is small; thus, patients should rec eive a dose that minimizes the risk of toxicity. For patients with new onset atrial fibrillation, other agents may be preferable for rate co ntrol. (C) 1998 by Excerpta Medica, Inc.