We are actually studying this drug right now in our Pharm class, and here is what our instructor says:
Any drug that is used to treat a dysrhythmia can CAUSE as dysrhythmia.
It has a long range of action (takes awhile to work), and the therapeutic leve is very, very close to the toxic dose of the drug.
The rationale, according to my instructor, is if someone is experiencing bradycardia or tachycardia, and you give digoxin, it can actually make the situation worse...especially if it's any doses after the initial has been given, because of the long range, means that the heart (if heading to one of the two extremes) still has not experienced the full effects of the last dose.
In our book, it states to not only hold but to call the HCP.
Disclosure: I'm a student...but I'm sure the experts will tell me how I did