Digitoxin and digoxin are both cardiac glycosides with similar pharmacodynamic effect.
Digoxin and digitoxin are both cardiac glycosides derived from the foxglove plant (Digitalis), but they have important differences in their pharmacokinetics and clinical use:
They have positive inotropy, negative chronotropy, and AV nodal conduction slowing
They differ significantly in their pharmacokinetics and clinical use.
Digoxin is less lipophilic, has lower protein binding (~20–30%), a shorter half-life (36–48 hours), and is primarily eliminated unchanged by the kidneys.
Its serum levels are highly dependent on renal function, and accumulation/toxicity is more likely in renal impairment, necessitating dose adjustment.
Digitoxin is highly lipophilic, extensively protein-bound (>95%), and has a much longer half-life (5–7 days).
Digitoxin is metabolized in the liver and eliminated via enterohepatic circulation and feces, making its clearance largely independent of renal function.
Thus, digitoxin is preferred in patients with significant renal dysfunction, as its serum concentrations remain stable without dose adjustment in renal impairment.
The risk of toxicity is higher with digoxin, especially in the elderly and those with renal dysfunction.
There is a lower incidence of toxicity with digitoxin compared to digoxin in hospitalized elderly patients.
Both drugs are used for heart failure and rate control in atrial fibrillation, but digoxin is more widely available and commonly used.
Digitoxin may be advantageous in patients with renal impairment.
Digoxin dosing must be individualized based on renal function, age, and concomitant medications.
Typical maintenance doses ranging from 0.125 to 0.25 mg daily.
Digitoxin dosing is less affected by renal function, and dose adjustments are generally not required in renal impairment.
Both drugs require careful monitoring for toxicity.
Digoxin is more commonly used in clinical practice.
Shorter half-life (36-48 hours)
Primarily eliminated by the kidneys
Requires dose adjustment in kidney disease
Less protein-bound (~25%)
Narrower therapeutic window
More frequent dosing may be needed
Digitoxin
Less commonly used today
Much longer half-life (4-6 days)
Primarily metabolized by the liver
Preferred in patients with severe kidney disease
Highly protein-bound ~90-95%
May be easier to maintain steady levels due to long half-life
Less frequent dosing required
Can accumulate more readily, making toxicity management challenging
Both drugs work by inhibiting the sodium-potassium ATPase pump, leading to increased intracellular calcium and improved cardiac contractility.
They’re used for heart failure and certain arrhythmias like atrial fibrillation.
The choice between them typically depends on the patient’s kidney function.
Digoxin is usually preferred due to more predictable pharmacokinetics and extensive clinical experience, while digitoxin might be considered in patients with significant renal impairment where hepatic metabolism is preferred over renal elimination.
Both require careful monitoring due to their narrow therapeutic windows and potential for serious toxicity.