Digoxin (plasma measurements)

In patients taking fixed daily dosage, steady state plasma concentrations vary widely making measurement desirable.

Therapeutic range (for 6 to 12h post dose) is 1.0 to 2.6nmol/l. Steady state occurs within 7 to 10 days (1).

Note that toxicity may occur with a level of less than 1.3nmol/l if there is hypokalaemia.

Features of toxicity include:

• cardiac: especially ectopic arrhythmias and heart block, particularly in combination
  
  
• non-cardiac effects: nausea, vomiting, anorexia, and (particularly in the elderly), diarrhoea, Occasionally confusion and delirium can occur. Colour vision abnormalities are rare

Reference:

1. Doctor (1/8/2002), 34.
2. British Heart Foundation (Factfile 7/2001). The use of digoxin.