Digoxin toxicity

Q: Patients with documented digoxin toxicity who receive Fab fragments should be observed in ICU for how long?

A) At least 24 hours
B) At least 48 hours
C) At least 72-96 hours
D) Once digoxin level is normalized
E) Once Fab fragment is received patient is safe to be monitored on Telemetry floor


Answer: C

Objective of above question is twofold:

1. Despite getting Fab fragments, recurrent digoxin toxicity with ventricular arrhythmia continue to occur for 72-96 hours  due to digoxin's large volume of distribution. This is particularly important in patients with renal dysfunction 1.

2. Once patient receives Fab fragments, laboratory cannot read digoxin level properly and any measurement for at least seven days would be erroneous. (Choice D) 2.


References:  

1. Renard C, Grene-Lerouge N, Beau N, et al. Pharmacokinetics of digoxin-specific Fab: effects of decreased renal function and age. Br J Clin Pharmacol 1997; 44:135. 

2.  Ujhelyi MR, Green PJ, Cummings DM, et al. Determination of free serum digoxin concentrations in digoxin toxic patients after administration of digoxin fab antibodies. Ther Drug Monit 1992; 14:147.