From the Guidelines
Digoxin levels should be maintained between 0.5 to 1.0 ng per mL for optimal efficacy and safety in patients with heart failure. This recommendation is based on the 2009 ACCF/AHA Heart Failure Guidelines 1, which suggest that doses of digoxin achieving a concentration of drug in plasma in this range are associated with the best outcomes.
Key Considerations for Digoxin Level Management
- The therapeutic range of 0.5 to 1.0 ng per mL is recommended due to the limited evidence available, and retrospective analyses suggesting that higher concentrations do not offer superior outcomes and may increase the risk of toxicity 1.
- Plasma concentrations exceeding 1.0 ng per mL have been associated with increased risk-adjusted mortality, although this may also reflect the severity of heart failure rather than a direct effect of digoxin 1.
- Monitoring of digoxin levels is crucial, especially when initiating therapy, changing doses, or when patients are at risk of toxicity due to factors such as renal impairment, electrolyte imbalances, or drug interactions 1.
Factors Affecting Digoxin Levels and Toxicity
- Renal function: Digoxin is primarily eliminated by the kidneys, and impaired renal function can lead to elevated serum digoxin levels and increased risk of toxicity 1.
- Electrolyte imbalances: Hypokalemia, hypomagnesemia, and hypothyroidism can potentiate digoxin toxicity, even at lower serum concentrations 1.
- Drug interactions: Concomitant use of certain medications like amiodarone, clarithromycin, erythromycin, itraconazole, cyclosporine, verapamil, or quinidine can increase serum digoxin concentrations and the risk of toxicity 1.
Practical Considerations for Digoxin Therapy
- Therapy with digoxin should be initiated and maintained at a dose of 0.125 to 0.25 mg daily, with lower doses (0.125 mg daily or every other day) recommended for patients over 70 years old, those with impaired renal function, or low lean body mass 1.
- There is no need for loading doses of digoxin to initiate therapy in patients with heart failure, and higher doses are rarely needed or used 1.
From the FDA Drug Label
About two-thirds of adults considered adequately digitalized (without evidence of toxicity) have serum digoxin concentrations ranging from 0.8 to 2. 0 ng/mL. About two-thirds of adult patients with clinical toxicity have serum digoxin concentrations greater than 2.0 ng/mL.
The therapeutic digoxin level is between 0.8 and 2.0 ng/mL for adults without evidence of toxicity. However, digoxin may produce clinical benefits even at serum concentrations below this range.
- Serum concentrations below 2.0 ng/mL do not rule out the possibility that a certain sign or symptom is related to digoxin therapy.
- Serum concentrations above 2.0 ng/mL increase the likelihood of digoxin intoxication. 2
From the Research
Digoxin Level
The therapeutic level of digoxin is generally considered to be between 0.5-0.9 ng/mL, with the upper limit being 2.0 ng/mL 3.
Factors Affecting Digoxin Levels
Several factors can affect digoxin levels, including:
- Age: Older patients may be more susceptible to toxic levels of digoxin 3, 4
- Renal function: Patients with renal dysfunction may require lower loading doses of digoxin to avoid toxicity 4
- Electrolyte levels: Abnormal levels of potassium, sodium, and calcium can increase the risk of digoxin toxicity 3
- Diabetes mellitus: Patients with diabetes may be more likely to have higher digoxin levels 3
Monitoring Digoxin Levels
Regular monitoring of digoxin levels is important to ensure that the patient is within the therapeutic range and to minimize the risk of toxicity 3, 5, 6, 7.
- Inpatient monitoring: Only 16% of inpatient digoxin levels were found to be appropriate, with daily routine monitoring being the primary reason for inappropriate testing 6
- Outpatient monitoring: 52% of outpatient digoxin levels were found to be appropriate, with early routine monitoring being the primary reason for inappropriate testing 6
Target Digoxin Levels
The target digoxin level is generally considered to be between 0.5-0.9 ng/mL, with levels above 2.0 ng/mL being considered toxic 3, 7.