Digoxin is a first-line drug of choice in patients with heart failure. The problem is that the side effects of digoxin are very frequent and dangerous. That is why it is a drug for hospital use with a narrow therapeutic margin. A drug with a narrow therapeutic margin is one that has a difference between the toxic dose and the very small therapeutic dose, and therefore its blood levels must be continuously monitored.
Digoxin, which is extracted from the Digitalis lanata plant , is a cardiotonic glycoside, which in addition to being used in situations of heart failure, is also indicated in patients with arrhythmias. However, its use is contraindicated in other cardiac disorders such as atrial fibrillation.
What is heart failure?
To understand how it works and what are the side effects of digoxin we must know the pathology for which it is indicated. Therefore, below we explain in a brief and simple way what heart failure is.
Heart failure is a syndrome characterized by a set of symptoms and signs secondary to a decrease in ventricular contractile function, the function of the heart valves or the loading conditions or the ventricles. This anomaly causes dyspnea (difficulty breathing), asthenia (weakness to carry out daily tasks), edema, oliguria (decreased urine formation), dizziness, etc.
When a person suffers from heart failure, their heart is unable to maintain the adequate volume pumped per minute in relation to venous return and the tissue needs of each moment. That is, it does not pump enough blood for the body to function normally.
Classification of heart failure
In this situation, we can distinguish three types
- Systolic heart failure. Decrease in cardiac output due to deterioration of the contractility of the heart. It is characterized by a decrease in the ejection fraction (blood that is expelled from the heart in relation to that which arrives) and cardiomegaly (an increase in the size of the heart).
- Diastolic heart failure. It is produced by a difficulty in ventricular filling due to failure of relaxation or mechanical obstruction of cardiac flow. In this situation, systolic function is preserved.
- Latent heart failure. It appears when there is a decrease in systolic ventricular function that does not occur with symptoms.
- Acute heart failure. If symptoms appear in minutes or hours and causes arterial occlusion and cardiotoxicity.
- Chronic heart failure. It develops in months or years. This type causes high blood pressure, heart disease, and other symptoms.
Digoxin side effects
Digoxin is a drug that is usually given intravenously. It accumulates in the tissues of the skeletal muscle, liver, kidney and heart. As we have already mentioned, it is a drug with a narrow therapeutic margin whose therapeutic concentrations range between 0.5-2 ng / ml.
When the concentration in the blood exceeds these values, the patient may suffer a condition known as digitalis poisoning. This toxic picture is characterized by a series of symptoms that we can classify into clinical cardiac signs and extracardiac signs.
Cardiac clinical signs
This symptomatic picture is developed by a series of alterations in the electrocardiogram. It is due to the presence of arrhythmias, both ventricular and atrial, sinus bradycardias or cardiac arrest. Due to these symptoms, the administration of digoxin is contraindicated in patients with supraventicular arrhythmias, suffering from atrio-ventricular block, as well as those suffering from diastolic heart failure and chronic uncontrolled hypokalemia.
As the name suggests, these symptoms are those that do not affect the heart, but other functions of the body. We can classify them into the following:
- Digestive. Nausea, diarrhea or vomiting.
- Jittery. Patients may experience depression, disorientation, dizziness, or headaches.
- Visual disturbances. They occur in 25% of patients with digoxin poisoning. We can highlight blurred vision, as well as the possibility of seeing flickering lights or red-green color blindness.
Other side effects of digoxin that have been reported include hallucinations and psychosis. On the other hand, hypersensitivity and thrombocytopenia (decreased number of platelets) are rare adverse reactions, but they can also develop.
Digoxin Side Effects: Final Comments
When the patient suffers from any of the above symptoms, both cardiac and extracardiac, treatment with digoxin should be stopped immediately. Next, the levels of the drug in the blood should be determined and potassium administered, since it is the antidote.