Digitalis therapy is a type of medical treatment for heart conditions that uses drugs made with chemicals from plants of the genus Digitalis. It is used to treat some types of arrhythmia, or abnormal heart rhythm, and heart failure. Digitalis therapy is usually administered orally, through pills or liquids prescribed by a doctor, though in an emergency it can also be intravenously injected. Due to the potentially serious side effects of digitalis medication and the resulting risks of digitalis therapy, its use has declined in recent years, but it is still commonly used for patients for whom other heart medications, such as beta blockers, have not been effective.
The genus Digitalis is a group of flowering plants, commonly referred to as foxglove. The most common source is the Digitalis lanata plant. Some plants of the genus contain large quantities of chemicals called cardiac glycosides, which are extracted for medical use. These are organic molecules, made up of a sugar bonded to an additional functional group, that strengthen the contractions of the cardiac muscles in the heart. The term “digitalis” is often used to refer collectively to all heart medications derived from these plants.
Digitalis is used to treat the heart conditions atrial fibrillation, atrial flutter, and congestive heart failure. Atrial fibrillation is a type of a arrhythmia that occurs when the contractions of the upper chambers of the heart, called the atria, are not properly synchronized with each other. This results in a rapid, irregular heartbeat that can cause palpitations and shortness of breath, along with damage to the heart that can eventually result in stroke or circulatory shock. Atrial flutter is an abnormally fast heart rate caused by abnormalities in the propagation of electrical impulses in the upper chambers of the heart that can lead to blood clots or stroke. Congestive heart failure, which can have a number of different causes, means that the heart is not able to supply sufficient blood to the body.
In each of these cases, the cardiac glycosides in digitalis cause an increase in the amount of calcium ions in the cells of the heart. This affects the transmission of electrical impulses through the heart, causing stronger, slower contractions of the cardiac muscle tissue. This improves the heart's ability to pump blood through the body and controls the rapid, uncoordinated atrial contractions that cause atrial fibrillation and flutter.
The most frequently used drug for digitalis therapy, made from Digitalis lanata, is called digoxin (C41H64O14). It is commercially sold under several trade names, including Digitek®, Lanoxin®, and Lanoxicaps®. Digoxin is usually taken orally in the form of 125 or 250 microgram tablets. Due to the risk of digitalis toxicity, the patient's blood chemistry needs to be carefully monitored so that the patient's physician can adjust dosage levels if needed.
The cardiac glycosides used in digitalis therapy can have serious side effects at excessive levels, including digestive issues such as vomiting or diarrhea, mental symptoms such as confusion and anxiety, and potentially lethal cardiac arrythmia. The amount of the drug that accumulates in the patient's bloodstream as the result of a particular dosage can vary greatly from patient to patient due to factors such as weight and kidney function, and the same amounts can have varying affects according to the patient's tolerance of the drug. The risk of toxicity is further increased by the fact that digitalis-derived drugs have a narrow therapeutic index, which means that they start to become toxic at levels that are only slightly higher than the level necessary for their medical benefits to occur.