A case series of hospitalized patients with elevated digoxin levels.
OBJECTIVE
Although there is renewed enthusiasm for the use of digoxin in patients with heart failure, current dosing guidelines are based on a nomogram published in 1974. We studied the incidence of and risk factors for elevated digoxin levels in patients admitted to a community hospital, and compared their dosage regimens to published guidelines.


METHODS
We reviewed the charts of all patients who had serum 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 levels. Of the 82 patients with complete records and correctly timed digoxin 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 had greater serum creatinine levels (3.1 +/- 7.3 versus 1.4 +/- 0.3 mg/dL; P = 0.01) than those with levels < or =2.4 ng/mL. Forty-seven patients had elevated digoxin levels on admission, including 21 patients admitted for digoxin toxicity. Impaired or worsening renal function contributed to high levels in 37 patients, and a drug interaction was a contributory factor in 10 cases. Twenty (43%) of these patients were taking the recommended maintenance dose based on the scheme employed in the Digitalis Investigation Group study. Thirty-five patients developed high digoxin levels while in hospital. In 26 patients, this followed a loading dose of digoxin for the control of rapid atrial fibrillation. Impaired renal function was implicated in all of these patients. Despite the elevated digoxin level, rate control was achieved in only 11 patients of these patients.


CONCLUSIONS
Elevated digoxin levels and clinical toxicity remains a common adverse drug reaction. Elderly patients, particularly those with impaired renal function and low body weights, are at the greatest risk. As published digoxin nomograms often result in toxicity, clinical variables need to be monitored. In patients with congestive heart failure and normal sinus rhythm the potential benefit of digoxin is small; thus, patients should receive a dose that minimizes the risk of toxicity. For patients with new onset atrial fibrillation, other agents may be preferable for rate control.
Marik
P E
PE
Medical Intensive Care Unit, St. Vincent Hospital, Worcester, Massachusetts 01604, USA.
Fromm
L
L
D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000139:chemically induced; D001281:Atrial Fibrillation / Q000150:complications / Q000188:drug therapy; D016009:Chi-Square Distribution; D003404:Creatinine / Q000097:blood; D004077:Digoxin / Q000008:administration & dosage / Q000009:adverse effects* / Q000097:blood*; D004347:Drug Interactions; D016903:Drug Monitoring; D004562:Electrocardiography; D005260:Female; D006333:Heart Failure / Q000150:complications / Q000188:drug therapy; D006760:Hospitalization; D006801:Humans; D007674:Kidney Diseases / Q000139:chemically induced / Q000175:diagnosis; D008297:Male; D012307:Risk Factors
D004077:Digoxin; D003404:Creatinine