Cardiac glycosides are organic compounds that act on the contractile force of the heart muscle. They are incredibly forceful in disrupting the operations of the heart, and thus most are very toxic if not entirely lethal. However, in recent years some cardiac glycosides have been adapted as a treatment for heart conditions such as congestive heart failure and cardiac arrhythmia. They increase the contractile force of the heart muscle, thus generating greater cardiac output - which is exactly what's needed in cases of heart failure.
There are three main cardiac glycosides available for use in the United States:
Of those, digoxin is the one most commonly used in the U.S. Ouabain is used primarily for research purposes.
Cardiac glycosides are used to treat heart conditions. They boost the power of the heart muscle, and thus enable it to continue working when it has been significantly weakened by a condition. While there are newer and more effective treatments available for most of the conditions treated by cardiac glycosides, they remain to be used widely. These drugs also have a slight diuretic effect on the kidneys, which is beneficial for most heart failure patients. Cardiac glycosides can also be used to treat atrial fibrillation and flutter by activating vagal efferent nerves to the heart. This slows down the ventricular rate and thus evens out the fibrillation to the regular rate.
Cardiac glycosides are contraindicated in patients who are hypokalemic, have atrioventricular block, or who have Wolff-Parkinson-White syndrome. Patients with impaired renal function may experience higher plasma levels while taking cardiac glycosides due to the fact that the medication is eliminated from the body through the liver. This is especially prevalent amongst lean, elderly patients because their renal function is most likely to be impaired. The most common side effect of cardiac glycosides is:
A number of commonly used drugs react with cardiac glycosides. The most common conflict is with drugs such as quinidine, calcium-channel blockers, and nonsteroidal anti-inflammatory medicines. These medications, when used with cardiac glycosides, can increase digoxin levels to a dangerous degree. The drug amiodarone also reacts strongly with cardiac glycosides, as do most beta blockers. Diuretics can sometimes interact indirectly. As with any medication, anyone thinking of taking cardiac glycosides should consult with their doctor about what they can and cannot take during treatment.
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