Evaluation of digoxin concentration after loading dose in patients with renal dysfunction

Area of Science:

• Pharmacology
• Nephrology
• Clinical Pharmacy

Background:

• Digoxin loading dose is based on volume of distribution and lean body weight.
• Maintenance dose is dependent on renal function.
• Volume of distribution is reduced in renal dysfunction, but the threshold for loading dose reduction is unknown.

Purpose of the Study:

• To describe digoxin loading practices at The Ottawa Hospital.
• To determine the incidence of digoxin toxicity after loading dose based on renal function.

Main Methods:

• Retrospective chart review of patients receiving digoxin loading dose (May 2008 - Jan 2012).
• Blood samples drawn 6-24 hours post-dose for digoxin concentration.
• Patients categorized into four groups based on creatinine clearance.

Main Results:

• Creatinine clearance below 60 mL/min predicted increased likelihood of toxic digoxin concentrations (OR 2.60).
• Mean loading doses varied by renal function group, with lower doses in severe dysfunction.
• Patients with creatinine clearance < 60 mL/min were more likely to experience toxic levels.

Conclusions:

• Current digoxin loading dose strategies pose a risk of toxicity in patients with creatinine clearance < 60 mL/min.
• Recommended reduction of digoxin loading dose to 6-10 μg/kg for these patients.
• Further trials needed to assess clinical implications and optimal doses for severe renal dysfunction (CrCl < 30 mL/min).