A concurrent audit of high digoxin plasma levels

Area of Science:

• Pharmacology
• Clinical Toxicology
• Nephrology

Background:

• Digoxin is a critical medication for heart conditions, but its narrow therapeutic index necessitates careful monitoring.
• Elevated digoxin levels can indicate toxicity, but other factors may influence interpretation.
• Understanding factors affecting digoxin levels and toxicity is crucial for patient safety.

Purpose of the Study:

• To audit patients with elevated digoxin levels to assess toxicity and identify contributing factors.
• To evaluate the impact of renal function on digoxin toxicity risk.
• To compare measured digoxin levels with pharmacokinetic predictions.

Main Methods:

• Concurrent audit of 92 patients with plasma/serum digoxin levels ≥ 3.0 ng/ml.
• Assessment of clinical evidence for digoxin toxicity.
• Analysis of factors including blood sampling time and renal function (creatinine clearance).
• Comparison of measured digoxin levels with weight- and creatinine clearance-based pharmacokinetic predictions.

Main Results:

• Digoxin toxicity was evident in 44 patients.
• Premature blood sampling explained high levels in 30 non-toxic patients.
• 14 patients tolerated high digoxin levels without adverse effects.
• Impaired renal function increased toxicity risk despite similar digoxin levels.
• Pharmacokinetic predictions frequently deviated from measured digoxin levels.

Conclusions:

• Digoxin toxicity assessment requires consideration of sampling time and renal function.
• Impaired renal function is a significant risk factor for digoxin toxicity.
• Current pharmacokinetic models may not accurately predict digoxin levels in all patients.