What is Digitalis Toxicity (Toxic Levels of Digoxin)?
Digoxin is a well-established heart medicine and one of the oldest used in heart health. It offers a broad range of positive effects and remains important in the modern treatment of suitable patients with heart failure and an irregular heartbeat known as atrial fibrillation. While digoxin is generally safe, it must be used at the correct dose. Doctors need to consider factors such as the patient’s age, sex, kidney health, and use of other drugs to prevent potentially dangerous side effects.
In the past 20 years, the use of digoxin has noticeably decreased and cases of negative reactions are uncommon. The rare instances that do occur are typically treated with a specific medicine that counters the effects of digoxin.
What Causes Digitalis Toxicity (Toxic Levels of Digoxin)?
Digitalis, a medicine developed from the foxglove plant, has been in use since 1785.
Taking too much of this medication can cause poisoning, as can long-term use, especially if the kidneys aren’t working properly.
Some metabolic conditions, like low potassium levels (hypokalemia) or high calcium levels (hypercalcemia) can increase the risk of digitalis poisoning, as can some drug interactions.
Chronic poisoning is more common than acute, or sudden, poisoning.
The most common cause of poisoning from digitalis is low potassium levels, often seen in people taking water pills (diuretics). Dosage mistakes are another common cause, especially in younger people.
Certain factors can increase the risk of poisoning from digitalis. These include:
- Having an underactive or overactive thyroid
- Being older in age
- Having a heart attack (MI)
- Having poor kidney function
- Having high calcium levels
- Having too much base (alkalosis) or not enough oxygen (hypoxemia) in your blood
- Having too much acid (acidosis) in your body
Several medications are linked to an increased risk of digitalis poisoning. These include:
- Diuretics (water pills)
- Heart rhythm medication Amiodarone
- Beta-blockers, used for high blood pressure
- Benzodiazepines, a type of tranquilizer
- Calcium channel blockers, for high blood pressure and heart conditions
- Macrolide antibiotics
- Propylthiouracil, used for an overactive thyroid
- Amphotericin, a type of antifungal medication
Risk Factors and Frequency for Digitalis Toxicity (Toxic Levels of Digoxin)
Over the years, digoxin, a medicine used to treat different heart conditions, has been used less frequently. Consequently, the occurrence of digoxin toxicity, which is when the drug causes harmful effects, has also been reducing. This decrease can also be linked to the advancements in technology that allow better monitoring of digoxin levels in the body, as well as a better understanding of how it interacts with other drugs. But it’s important to note that digoxin is still widely used and can be toxic if taken in incorrect amounts, which continues to pose a serious issue.
- Use of digoxin has decreased over time which resulted in lower instances of digoxin toxicity.
- Improvements in technology and understanding of drug interactions have also helped avoid toxicity.
- Despite the reduction, digoxin is still widely used and can be harmful if not taken correctly.
- In 2011, according to United States poison control data, 2513 cases of digoxin toxicity were reported, with 27 of these cases resulting in death.
Signs and Symptoms of Digitalis Toxicity (Toxic Levels of Digoxin)
If a person has been exposed to a poisonous substance, it’s crucial to establish if the poisoning is acute (sudden) or chronic (over a prolonged period). Most poisonings that are reported are due to chronic toxicity.
Symptoms of poisoning can vary and include issues with the gut, nerves, and heart. Most commonly, people may experience headaches, fatigue, difficulty sleeping, confusion, abdominal pain, and nausea and vomiting. A unique symptom of a specific type of poisoning known as digitalis toxicity is seeing a yellow tint in your vision. Heart problems can also occur, causing irregular heart rhythms and rhythm disturbances. In some cases, people may also find light unbearable, see flashes of light, or have reduced visual sharpness.
- Chronic exposure to poisonous substances can lead to poisoning
- Common symptoms include headaches, fatigue, sleeping difficulties, confusion, abdominal pain, and nausea and vomiting
- Yellow-tinted vision is a unique sign of digitalis toxicity
- Irregular heart rhythms and rhythm disturbances may occur
- Other visual problems could include sensitivity to light, seeing light flashes, or decreased visual acuity
Digoxin toxicity doesn’t have a specific heart rhythm abnormality associated with it, but a range of abnormal heart rhythms can be detected such as varying degrees of AV block (a delay or blockage in the signals from the upper chambers of the heart to the lower chambers), premature heartbeats originating from the lower chambers of the heart, slow heart rate, and even fast heart rhythms arising from the lower chambers of the heart. The primary cause of death in those with digoxin toxicity is abnormal heart rhythms.
Some patients with poisoning may have unstable vital signs depending on the type of heart rhythm abnormality they have, while others may experience difficulty breathing and altered mental status.
Testing for Digitalis Toxicity (Toxic Levels of Digoxin)
Digoxin is a type of medicine with a small therapeutic range, which is the beneficial zone for which it works best, established at between 0.5 and 2 ng/mL. When diagnosing whether someone is having a toxic reaction to the drug, it’s hard to tell and often relies on signs and symptoms, rather than just blood levels of digoxin. This is because the amount of digoxin in the blood doesn’t always relate directly to toxicity.
Digoxin is mainly eliminated by the kidneys, so if the kidneys aren’t working too well, it can lead to a buildup of the drug and turn into chronic toxicity. That’s why it’s essential to check kidney function. The levels of electrolytes, which are types of salts in your body, need to be monitored too. If you have low levels of potassium or magnesium, or high levels of calcium, it can enhance the harmful effects of digoxin toxicity.
Furthermore, digoxin affects sodium and potassium levels in your body, leading to high potassium levels, a condition known as hyperkalemia. This can serve as an indicator of the severity of drug toxicity.
To keep track of how the drug is affecting your heart, it is recommended to have continuous cardiac monitoring or regular electrocardiograms (EKGs). That’s because it can change your heart rhythms. EKGs might show changes like flat T waves or a scooped appearance in the ST-segment, often referred to as the ‘Digitalis effect’.
There are also factors that can give a false-positive result when testing for digoxin, which can give the impression of toxicity even when the levels are not dangerous. This is more likely to happen if you have liver or kidney disease, chronic heart failure, hemorrhage under your skull, acromegaly (a hormone disorder), diabetes, or if you are pregnant.
The way we measure digoxin levels and its breakdown products varies in sensitivity and can sometimes be thrown off by similar substances like steroids and cholesterol-like substances, making it even more challenging to accurately diagnose toxicity.
Treatment Options for Digitalis Toxicity (Toxic Levels of Digoxin)
Treatment for digoxin toxicity starts with an accurate and timely diagnosis, followed by the administration of specific anti-digoxin antibodies, commonly known as Fab fragments. While the concentration of digoxin in the body does not always directly tie to the symptoms, it can be helpful in figuring out how much of the antidote to give.
The use of digoxin immune Fab, also known by the brand name Digibind, is considered the first course of treatment for heart rhythm problems, including AV block and ventricular tachycardia, caused by suspected digoxin toxicity. These antibody fragments effectively attach to the digoxin molecules and are then expelled through urine, with minimal negative side effects. Doctors typically start with 10 vials of Fab fragments for adults and five vials for children.
However, doctors must be careful because this treatment can lower the amount of potassium in the blood, which requires regular monitoring. If a person has just ingested digoxin, activated charcoal might be used within the first two hours. Beyond that, the patient will receive supportive care.
It’s important to remember that neutralizing the digoxin with antibodies can lead to heart failure and worsening heart rhythm problems. There can also be side effects from the antibodies, such as serum sickness and severe allergic reactions.
While the patient is undergoing treatment, their heart rhythm needs to be continuously watched. Any issues with electrolytes in the blood need to be corrected. Some heart rhythm problems might require the use of short-acting beta-blockers, phenytoin, or lidocaine, while atropine can be used for slow heart rhythms. However, magnesium is not recommended as it can worsen slow heart rhythms or an AV block. If needed, defibrillation might be used according to established guidelines.
Maintaining hydration and oxygen levels is also vital to the patient’s treatment. More research is needed to determine optimal dosing and cost-effectiveness of using digoxin-specific antibodies for non-life-threatening cases.
What else can Digitalis Toxicity (Toxic Levels of Digoxin) be?
Conditions which can affect your kidney function or cause harm to your heart and overall health include:
- Acute kidney injury
- Excessive use of beta-blockers (heart medication)
- Excessive use of calcium channel blockers (high blood pressure medication)
- Hypercalcemia (high calcium levels)
- Hyperkalemia (high potassium levels)
- Hypernatremia (high sodium levels)
- Hypoglycemia (low blood sugar)
- Hypokalemia (low potassium levels)
- Hyponatremia (low sodium levels)
These conditions require medical attention and can be detected through blood tests.
What to expect with Digitalis Toxicity (Toxic Levels of Digoxin)
The outcome of a patient’s condition often depends on the timing of their medical help, their age, and any other existing health conditions. The risk of death can increase if heart blockages or new irregular heart rhythms are involved with the patient’s toxicity. Despite receiving the best care possible, between 1-5% of patients may still unfortunately pass away.
Possible Complications When Diagnosed with Digitalis Toxicity (Toxic Levels of Digoxin)
Potential health risks include:
- Heart failure
- Nodal block
- Anaphylaxis (severe allergic reaction) associated with the medication digibind
Preventing Digitalis Toxicity (Toxic Levels of Digoxin)
Make sure to avoid any possible drug interactions. Regularly check how well your kidneys are working. Keep an eye on the levels of Digoxin in your system. If possible, try not to use Digoxin. Also, it’s important to regularly monitor the levels of minerals and salts (electrolytes) in your body.
