Derived from the purple foxglove plant, Digoxin was first used to treat heart complaints 200 years ago. Dr Ross McGeoch, Consultant Interventional Cardiologist at Hairmyres Hospital, tells Senior Cardiac Nurse Christopher Allen about modern uses for the drug.
Why have I been prescribed this medication?
Most commonly, we use digoxin to treat abnormal heart rhythms (arrhythmias), including atrial fibrillation, as part of a treatment plan to slow the heart rate. The aim is to reduce the strain the heart is under because, over time, this can wear out the heart muscle and lead to heart failure.
For those who already have a degree of heart failure, it can also be useful in decreasing the level of strain on their heart. At present, however, it’s more common that you’d be given a beta blocker, such as bisoprolol, or a calcium channel blocker, such as diltiazem, first.
Digoxin would usually be prescribed if you’re unable to tolerate these types of medications, or used in combination with them if you need a further reduction in your heart rate.
While digoxin may help to reduce your heart rate, it will not get your heart rhythm back to normal. Instead, this is done by other types of medications, such as amiodarone.
Digoxin can also be used in the late stages of heart failure, but this is becoming less and less common, because more effective drugs are available.
How does it work?
Digoxin is a type of drug called a cardiac glycoside. Their function is to slow your heart rate down and improve the filling of your ventricles (two of the chambers of the heart) with blood.
For people with atrial fibrillation, where the heart beats irregularly, a different volume of blood is pumped out each time. This means an irregular amount of vital oxygen is sent to the brain and the rest of the body, which can lead to symptoms like light-headedness and lethargy.
If you have heart failure, your heart muscle has become less effective at pumping blood around the body, so allowing it more time to fill with blood before it pumps can help to improve symptoms.
Is digoxin right for me?
If you have atrial fibrillation, it’s likely your beta blockers or calcium channel blockers will be increased to the maximum dose you can tolerate before your doctor considers digoxin. If this didn’t improve your symptoms or reduce your heart rate to an acceptable level, then digoxin may be added in.
Digoxin is occasionally given on its own if someone has permanent atrial fibrillation and is very physically inactive, according to NICE (National Institute for Health and Care Excellence) guidelines.
Similarly, if you have heart failure, it’s recommended that all other medications are given at the maximum dose you can tolerate before using digoxin. These usually include beta blockers, ACE (angiotensinconverting enzyme) inhibitors such as ramipril, and ARBs (angiotensin receptor blockers) such as candesartan.
Can I take digoxin with my existing heart medications?
Digoxin can interact with some common heart medications, including verapamil and amiodarone. If you’ve already been prescribed one of these, your doctor may choose alternatives or recommend you don’t start digoxin at all.
Are there side effects?
Digoxin can have side effects if you’re given the wrong dose, so it’s important to have regular tests to check the levels in your blood. You may also be tested if symptoms suggest there is too much digoxin in your blood (see below) or if you have kidney problems, as the drug is cleared from your body by the kidneys.
Side effects include nausea, vomiting, diarrhoea, tiredness, insomnia, visual disturbances, palpitations and fainting. In rare cases, increased levels of digoxin in your blood can cause heart rhythm disturbances (arrhythmias).
These are serious and require treatment as soon as possible. If you experience heart rhythm disturbances, you must go to A&E for an electrocardiogram (ECG) and a blood test.
Are there any adverse effects?
Recent studies have highlighted concerns about digoxin. If you have been prescribed it, it’s because your doctor has decided that benefits outweigh the risks for you.
“We’ve known that digoxin can be problematic for a long time, particularly when mixed with some other medications,” says Dr Mike Knapton, the BHF’s Associate Medical Director.
“This is why digoxin is only prescribed after careful consideration. The dose of digoxin is crucial as too little won’t help, but too much can cause nausea, vomiting and changes to the heart’s electrical system. People taking digoxin should get regular blood tests to ensure their levels of the drug are within carefully defined limits. When needed, it is still a powerful, useful drug.”
Digoxin is currently prescribed to hundreds of thousands of people in England and Wales. It isn’t usually first choice for irregular heartbeat or heart failure. You may be given it because you can’t tolerate another medication, or because you need additional treatment.
If you take digoxin and are worried about your health, speak to your doctor and make sure you should be on it, that the dose is correct and that you are being monitored adequately.