Arrythmias

[maninthemirror]

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Two questions. If you can answer either or both, much appreciated.

1) What is the mechanism by which digoxin cases hypokalemia?

2) Why does hypokalemia and/or hypomagnesia put you at a risk for Torsades de Pointes?

Thanks.

 

[Frank Nutter]

1. inhibits NaKATPase
2. prolongs repolarization, phase 3 and 4 I think, bigger window for EAD to occur and induce a triggered arrhythmia. Torsades is actually a reentry arrhythmia after the EAD is triggered.

 

[Charles_Carmichael]

I'm only an M1 and don't have a pharm/pathophys background, but why would digoxin cause hypokalemia? My understanding is that, if anything, it would cause hyperkalemia by inhibiting the Na+/K+ ATPase and preventing re-uptake of K+ into the cell.

 

[dr seuss]

It doesn't cause hypokalemia.

 

[SoundofSilver]

Hypokalemia can increase digoxin toxicity since potassium and digoxin compete for the same binding site on the sodium/potassium pump, but it does not cause hypokalemia as far as I know.

 

[OCallag]

It can cause diarrhea. That could cause hypokalemia...

 

[Bernoull]

Hypokalemia can increase digoxin toxicity since potassium and digoxin compete for the same binding site on the sodium/potassium pump, but it does not cause hypokalemia as far as I know.

this..

Also, does anyone know the mechanism of increased digoxin toxicity in hypomagnesia?

 

[Charles_Carmichael]

this..

Also, does anyone know the mechanism of increased digoxin toxicity in hypomagnesia?

My guess would be that, since ATP must be bound to Mg2+ in order to be biologically active, hypomagnesemia would also inhibit the Na/K pump activity (by decreasing the stores of biologically active ATP). That, combined with digoxin's inhibition of the Na/K pump, would result in increased toxicity.