Digoxin: 6 things you should know
Medically reviewed by C. Fookes, BPharm Last updated on Oct 29, 2018.
1. How it works
- Digoxin may be used in the treatment of heart failure or atrial fibrillation.
- Digoxin works by inhibiting an enzyme (called Na-K ATPase) responsible for the exchange of sodium for other electrolytes in cells. This, in turn, increases the amount of calcium that enters the heart, affecting the electrical system of the heart and ultimately the way the heart beats.
- Digoxin belongs to the class of medicines known as digitalis glycosides (may also be called cardiac glycosides).
- May be used in the treatment of mild-to-moderate heart failure. It improves left ventricular ejection fraction (which is the amount of blood pumped out of the heart with each beat) and improves symptoms of heart failure (such as exercise capacity) and reduces the number of hospitalizations.
- May also be used in the treatment of persistent atrial fibrillation (AF) to control the ventricular response rate (how fast the ventricles in the heart beat).
- Available in an injectable form for people requiring needing rapid digitalization or who cannot swallow oral tablets; however, intravenous injection is preferred because intramuscular injection can be extremely painful.
- Generic digoxin is available.
If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:
- A headache, weakness, dizziness, anxiety, abdominal pain, and with prolonged use, gynecomastia (breast enlargement in males).
- There is a fine line between toxic levels of digoxin and therapeutic levels. Factors such as body weight, age, kidney function, interacting medications, and potassium intake can all upset the balance, so ongoing monitoring of digoxin and electrolyte levels is required.
- Signs of toxicity include nausea, vomiting, visual disturbances, arrhythmia and weight loss.
- The dosage of digoxin requires adjusting in people with kidney disease.
- Digoxin is not suitable for some people with certain types of arrhythmia (such as ventricular fibrillation) and with some other types of cardiac disease.
- Digoxin interacts with several drugs, including antibiotics, atorvastatin, other heart medications, and indomethacin. See here for a full list of interactions.
- Regular monitoring of digoxin levels is necessary. However, a dosage adjustment should never be based on an isolated measurement of serum digoxin concentration as these can be falsely elevated by digoxin-like substances. Regular monitoring of potassium levels and kidney function is also necessary.
- Taking digoxin does not appear to increase or decrease a person's risk of death.
- Effects may be better when used in combination with a diuretic and an angiotensin-converting enzyme (ACE) inhibitor.
Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.
- May be taken with or without food.
- If taking digoxin liquid, carefully measure the dose using the dropper provided (do not use a normal household teaspoon because there is no guarantee you are getting the correct dose).
- Take as directed by your doctor. Do not increase or decrease the dosage without his or her advice.
- Your doctor may advise you to record your heart rate and blood pressure daily while taking digoxin.
- Some doctors may initiate digoxin dosing with a loading dose (a higher than normal dose) followed by a smaller, regular maintenance dose. Others may just choose to start with a regular maintenance dose - this means it will take a few days to reach effective blood levels. Any further dosage increases should happen at two weekly intervals to allow time for digoxin to reach peak levels.
- Digoxin may need to be temporarily stopped or reduced prior to electrical cardioversion. Your doctor will advise you about this.
- Your doctor needs to monitor your blood levels of digoxin regularly, and also your kidney function and potassium levels. Although there is an ideal range for digoxin levels in the blood (0.5-2 ng/mL), doctors should interpret your levels based on your response to the drug.
- Talk to your doctor or pharmacist before taking any other medication with digoxin, including medicine brought over-the-counter, because several medicines, including herbal medicines and supplements, can interact with digoxin.
- Seek immediate medical advice if you experience nausea or vomiting, persistent diarrhea, confusion, weakness, or visual disturbances (including blurred vision, green-yellow color disturbances, halo effect) because these may be a sign that your digoxin levels are too high.
- In infants, symptoms of high digoxin levels may differ from adults and include weight loss, failure to thrive, abdominal pain, and behavioral disturbances.
6. Response and Effectiveness
- Although some effects of digoxin may be noticed soon after taking, it can take up to 7-14 days or longer after drug initiation or a dosage change for the full effects to be seen.
- Digoxin levels of less than 0.5 ng/mL have been associated with reduced efficacy, while levels above 2 ng/mL have been associated with toxicity without increased benefit. However, digoxin levels should always be interpreted taking into account what effects the drug in having and any symptoms of toxicity.
- Digoxin [Package Insert] Revised 03/2018. General Injectables and Vaccines, Inc. https://www.drugs.com/pro/digoxin-injection.html
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use digoxin only for the indication prescribed.
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