Digoxin formulas

The digoxin model is not hard-coded into the program.  The parameters are found in the drug model database and are fully user-editable.  You can tailor each drug model to fit your patient population, or you can create your own models.  See the Edit drug models section of the help file for further information.

Initial dosing

1.  Estimate Volume of Distribution (Jusko Equation)

Vd =  226 + [(298 x CrCl) / (29.1 + CrCl)] x (BSA / 1.73)

 where CrCl = normalized creatinine clearance(ml/min)

BSA = Body surface area (square meters)

2.  Calculate Loading Dose

LD = Vd x Cp/F

where Vd = Volume of distribution (liters)

Cp = target serum level (mcg/l)

F = bioavailability factor:

• IV push = 1

• capsules= 0.95

• elixir = 0.8

• tablets = 0.75

3.  Estimate Clearance (Koda-Kimble)

Cl = [(A x CrCl) + B] x C        

where A = 0.88, for patient with Acute CHF, otherwise=1

B = 23, for patient with Acute CHF, otherwise=40

C = correction factor for interacting drugs:

• Quinidine = 0.65

• Spironolactone = 0.75

• Verapamil = 0.7

4.  Calculate Maintenance Dose

MD = (Cl x Cp x tau) / F        

where Cl = Clearance (liters/hour)

Cp = target serum level (mcg/l)

tau = dosing interval (hours)

F = bioavailability factor

5.  Estimate steady-state trough level

Cpss = (MD x F) / (Cl x tau)

where MD = Maintenance dose (mcg)

F = bioavailability factor

Cl = Clearance (liters/hour)

tau = dosing interval (hours)

Adjust maintenance dose

1.  Estimate Volume of Distribution (Jusko Equation - see above)

2.  Calculate digoxin clearance

Cl = [(MD x F) / Cp] / tau

where MD = Maintenance dose (mcg)

F = Bioavailability factor

Cp = Steady-state serum digoxin concentration (mcg/l)

tau = Dosing interval (hours)

3.  Calculate Maintenance Dose

MD = (Cl x Cp x tau) / F

where Cl = Digoxin clearance (l/hr)

Cp = target serum level (mcg/l)

tau = dosing interval (hours)

F = bioavailability factor

4.  Estimate steady-state trough level

Cpss = (MD x F) / (Kel x Vd x tau)

where MD = Maintenance dose (mcg)

F = bioavailability factor

Kel = Elimination rate (1/hours)

Vd = Volume of distribution (liters)

tau = dosing interval (hours)

See also:

Introduction

Monitoring parameters

Precautions

Bibliography