Potassium competes with Digoxin for binding to the Na-K ATPase pump in heart muscle cells.
When you have lowered potassium (hypokalemia) you get increased binding of Digoxin to the ATPase pump...and increase the risk of Digoxin toxicity [basically you have less competition for the pump and more Digoxin can perform on the pump].
So yes, hypokalemia, most definately increases the risk of Digoxin toxicity.
Many patients taking digoxin for heart failure will also be taking diuretics. If the diuretics are non-potassium sparing then you have a risk of getting hypokalemia quite easily.
And because of Digoxin's narrow safety window...changes in potassium levels can be very dangerous. The levels of this drug and the levels of potassium in the blood of patients taking it should be monitored closely.
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