Digoxin belongs to a group of drugs called cardiac glycosides. These medications are used to control heart rate and rhythm. Digoxin is extracted from the leaves of the plant Digitalis lanata. Digoxin is widely used to treat congestive heart failure and atrial arrhythmias (irregular heart rhythms that arise from the top chamber of the heart) such as atrial fibrillation, atrial flutter and atrial tachycardia.
Mechanism of Action
The National Library of Medicine's DailyMed website explains that digoxin has a direct effect on the cardiac muscle by slowing down the conduction system of the heart through inhibiting the exchange of sodium, potassium and calcium across myocardial (heart) cell membranes. Altering the exchange rate of these electrolytes slows the heart rate. The result is a stronger, more stable heart rate and rhythm.
Availability
Digoxin is available as a capsule, a tablet, an elixir and an injection. Use caution if you switch from the pill form to the elixir because the elixir is more readily absorbed into your system; you may need a smaller dose of elixir than your usual pill dose.
You may receive digoxin as an injection into a vein (intravenous) during a cardiovascular emergency such as when you have a very rapid heart rhythm caused by atrial tachycardia or atrial fibrillation. These conditions can elevate the heart rate so drastically that blood pressure drops very low and you may suffer chest pain, shortness of breath and loss of consciousness.
Considerations
Billie Ann Wilson, Ph.D., Margaret Shannon, Ph.D., and Kelly Shields, Pharm.D., authors of "Pearson Nurse's Drug Guide 2010," advise that when digoxin is given intravenously, 100 percent of the drug is absorbed; therefore, digoxin is administered slowly over five minutes and you are monitored for any adverse reactions such as a low heart rate, called bradycardia, or a condition called heart block, which can lead to cardiac arrest.
When taking digoxin at home, do not take over-the-counter medications without checking with your doctor in order to prevent drug-drug interactions. Measure your heart rate for one full minute before each dose; if your heart rate is less than 60 beats per minute or greater than 110 beats per minute, do not take your digoxin and call your doctor.
Common Effects
Greater than 1 percent of patients taking digoxin experience the following adverse effects: low blood pressure, bradycardia, nausea, fatigue and dizziness. These symptoms can be mitigated by dose adjustment. Nausea is improved by taking digoxin with food; however, drug absorption is affected by high-fiber foods, so eat these foods at a time other than when you take your digoxin.
Warning
Once patients have a therapeutic blood level of digoxin, they are said to be fully digitalized. At this point, the therapeutic effects of digoxin last three to four days; this prolonged duration of digoxin creates the danger of toxicity. Thus patients are closely monitored through lab draws that check levels of digoxin in the blood. Electrolyte levels are also closely monitored during digoxin therapy. Low potassium and magnesium levels increase the risk of digoxin toxicity.
References
- National Library of Medicine's DailyMed: Digoxin Tablet
- "Pearson Nurse's Drug Guide 2010"; B.A. Wilson, T.M. Shannon and K.M. Shields; 2010
