Digoxin in chronic atrial fibrillation

• in general, use digoxin orally (1) - intravenous administration is rarely justified; intramuscular administration is never justified
  
  
• loading dose (1):
  • if possible, start with a loading dose of approximately 15 mcg per kg of estimated LEAN body weight, given in 3 divided doses at 6 hourly intervals. For example, in woman who has a LEAN body weight of 50 kg then you would give a loading dose of 750 mcg (15x50), in three doses of 250 mcg each, 6 hours apart. If there is not a satisfactory slowing of ventricular rate, and there is no evidence of toxicity, then consider trying another 5 mcg/kg (in this case another 250 mcg). If this is ineffective then try another drug
    
    
• maintenance dose (1):
  • this is based on renal function:
    • creatinine clearance (CC) = 100ml/min; daily maintenance dose as a fraction of the effective loading dose (DMD) = 1/3
    • CC = 50ml/min; DMD = 1/4
    • CC = 25ml/min; DMD = 1/5
    • CC = 10 ml/min; DMD = 1/6
    • CC = 0 ml/min; DMD 1/7

Note that treatment with a loading dose in the way described requires careful monitoring during the early stages. If this is not possible then consider give a regular maintenance dose from the start. This would mean a maintenance dose of 5mcg per kg in a patient with a patient with normal renal function (1). However, it will take at least a week for this dosage to build up to an effective therapeutic amount in the body (longer in a patient with renal impairment), so this is a less ideal method of treatment (1).

Reference:

• (1) British Heart Foundation Factfile 7/2001. The use of digoxin.