Serum digoxin concentrations in canine congestive heart failure

Area of Science:

• Cardiology
• Pharmacology
• Veterinary Medicine

Background:

• Congestive heart failure (CHF) is a common condition in dogs.
• Digoxin is a cardiac glycoside used to treat CHF, but its narrow therapeutic index requires careful dosing.
• Accurate digoxin dosing is crucial to avoid toxicity and ensure efficacy.

Purpose of the Study:

• To evaluate the efficacy of a standard oral digoxin dosage regimen in dogs with CHF.
• To determine if adjustments for lean body mass and other pharmacokinetic factors improve digoxin serum concentrations within the therapeutic range.

Main Methods:

• Ten dogs with CHF received digoxin at 0.01 mg/kg lean body mass twice daily.
• Lean body mass was calculated by subtracting ascites and fat from gross mass.
• Doses were adjusted for renal/hepatic function, formulation bioavailability, and patient size.
• Serum digoxin concentrations (trough and peak) were measured after 10 days or upon toxicity onset.

Main Results:

• Six out of ten dogs exhibited serum digoxin concentrations in the toxic or subtherapeutic range.
• The standard dosing regimen, even with adjustments, provided only a rough approximation of the required dose.
• This suggests significant inter-dog variability in digoxin pharmacokinetics.

Conclusions:

• The oral digoxin dosage of 0.01 mg/kg lean body mass twice daily is unreliable for achieving therapeutic serum concentrations in dogs with CHF.
• Current dosing adjustments are insufficient to guarantee efficacy and safety.
• Further research into alternative dosing strategies, such as using body surface area, is warranted, though potential variability remains.