Digoxin Level

To obtain steady-state serum digoxin concentrations, blood samples should be drawn 6-8 hours after the daily dose or just prior to the next scheduled dose.

DIG

Lanoxin

Serum:  (RED)

Serum (Red) or Gold (SST) or Orange (OJ) or Tiger Top Serum
Light Green (PST) at FHSH

Slight hemolysis acceptable. Collect blood samples in SST/Gold or Red top collection tubes. Allow tubes to clot adequately before centrifugation. Keep tubes stoppered and upright at all times. Serum must be separated from the red blood cells within 2 hours post-centrifugation.

Room temperature for up to 8 hours. >8 Hours refrigerate at 2-8ºC. >48 hours freeze at -20ºC or colder. Samples can only be thawed once.

24x7

Therapeutic:   0.8-2.0 ng/mL
Critical/Toxic:   >2.5 ng/mL

Digoxin is a widely prescribed drug used in the treatment of congestive heart failure, atrial fibrillation, atrial flutter, supraventricular tachycardia, and other cardiac disorders. Treatment with digoxin results in more effective cardiac contractility, decrease in conduction velocity, and a slowing of the heart rate. The therapeutic range for digoxin is narrow. Desired effects become exaggerated with administration of an excess of digoxin leading to conditions difficult to distinguish from the original cardiac symptoms. Coupled with the narrow therapeutic to toxic range is a considerable variability in patient response to the same dose. In different patients identical doses of digoxin result in different serum levels mainly due to individual variation in myocardial sensitivity, absorption, diet, and excretion of the drug. The variability in bioavailability of different drug formulations and interactions with other drugs, particularly drugs affecting the electrolyte balance such as diuretics, also affect individual patient responses. Measuring a serum sample drawn 6–8 hours after the administration of digoxin allows for equilibration of serum and tissue digoxin levels. Monitoring digoxin levels can assist the physician in adjusting digoxin dosage.