How digoxin works
Digoxin belongs to the group of digitalis glycosides (such as digitoxin). All members of this group have the same action profile and differ only in how quickly and for how long they act in the body.
Digoxin blocks an enzyme in the cell membrane of the heart muscle cells, the so-called magnesium-dependent Na/K-ATPase. This enzyme transports sodium ions out of the cell and, in return, potassium ions into the cell.
The result is increased contractility of the heart muscles (positive inotropic effect). In addition, digoxin slows the heart’s beating rate (negative chronotropic effect), inhibits conduction (negative dromotropic effect) and increases the heart’s excitability (positive bathmotropic effect).
Absorption, degradation and excretion
Digoxin can be administered by mouth (orally) or directly into a vein (intravenously). When administered intravenously, the drug takes 15 to 30 minutes to take effect and reaches its maximum effect after 1.5 to 5 hours. With oral administration, the onset of action and the achievement of the maximum effect take slightly longer.
When is digoxin used?
Digoxin is prescribed for heart failure and certain forms of arrhythmia (such as atrial fibrillation).
How digoxin is used
Thereafter, a lower maintenance dose of usually 0.25 to 0.375 milligrams once daily is administered. However, the dose is always individually adjusted and monitored with regular plasma concentration determinations.
If kidney function is impaired, the dose is reduced and/or the interval between doses is extended.
What are the side effects of digoxin?
In men, enlargement of the mammary glands (gynecomastia) and liver dysfunction occur in rarer cases. Sometimes blood count changes such as a lack of platelets (thrombocytopenia) also develop.
What should be considered when using digoxin?
Contraindications
Digoxin must not be used in:
- hypersensitivity to the active substance or other cardiac glycosides
- excessively high calcium levels (hypercalcaemia)
- Hypertrophic obstructive cardiomyopathy (genetic heart disease with enlargement of the heart muscle)
- certain forms of cardiac arrhythmia (such as AV block grade II and III and WPW syndrome)
- concomitant use of intravenous calcium salts
Interactions
Other drugs can increase the bioavailability of cardiac glycoside in the body, for example certain antibiotics (such as tetracyclines, erythromycin). Some drugs decrease the excretion of digoxin, such as quinidine, amiodarone, verapamil and diltiazem (agents for cardiac arrhythmias), and spironolactone (diuretic).
Other interactions are possible, which the attending physician will take into account when prescribing.
Age restriction
Digoxin may be administered from birth if indicated.
Pregnancy and lactation
Cardiac glycosides such as digoxin may be used during pregnancy in cases of cardiac insufficiency and cardiac arrhythmias of the mother or the unborn child.
How to obtain medication with digoxin
Digoxin requires a prescription in Germany, Austria and Switzerland and is only available from pharmacies with a prescription.
