Digoxin vs. metoprolol: What's the difference?

What are digoxin and metoprolol?

Digoxin is a cardiac glycoside used to treat adults with mild to moderate congestive heart failure and to treat abnormally rapid atrial rhythms (such as atrial fibrillation, atrial flutter, and atrial tachycardia). Digoxin is also used to increase myocardial contractility in pediatric patients with heart failure. Digoxin increases the force of contraction of the heart muscle by inhibiting the activity of an enzyme (ATPase) that controls movement of sodium, calcium, and potassium into the heart muscle. Calcium controls the force of contraction. Inhibiting ATPase increases calcium in the heart muscle, which increases the force of heart contractions. Digoxin also slows electrical conduction between the atria and the ventricles of the heart, which is useful in treating abnormally rapid atrial rhythms.

Metoprolol is a beta-blocker (beta-adrenergic blocking agent) used to treat high blood pressure (hypertension), heart pain (angina), congestive heart failure, hyperthyroidism, abnormal heart rhythms, and some neurologic conditions. Metoprolol is used off-label to prevent migraine headaches. Metoprolol blocks the action of the sympathetic nervous system (a portion of the involuntary nervous system).

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What are the side effects of digoxin and metoprolol?

Digoxin

Common side effects include:

Many digoxin side effects are dose dependent and happen when blood levels are over the narrow therapeutic range. Therefore, digoxin side effects can be avoided by keeping blood levels within the therapeutic level. Serious side effects associated with digoxin include:

Digoxin has also been associated with visual disturbance (blurred or yellow vision), abdominal pain, and breast enlargement. Patients with low blood potassium levels can develop digoxin toxicity even when digoxin levels are not considered elevated. Similarly, high calcium and low magnesium blood levels can increase digoxin toxicity and produce serious disturbances in heart rhythm.

Metoprolol

WARNING:

  • In patients with existing slow heart rates (bradycardias) and heart blocks (defects in the electrical conduction of the heart), metoprolol can cause dangerously slow heart rates, and even shock. Metoprolol reduces the force of heart muscle contraction and can aggravate symptoms of heart failure. In patients with coronary artery disease, abruptly stopping metoprolol can suddenly worsen angina, and occasionally precipitate heart attacks. If it is necessary to discontinue metoprolol, its dosage should be reduced gradually over several weeks.
  • Initiation of high-dose extended release metoprolol in patients undergoing non-cardiac surgery is associated with bradycardia (slow heart rate), hypotension, stroke, and death. However, long-term therapy with metoprolol should not be routinely withdrawn prior to major surgery. Impaired ability of the heart to respond to reflex adrenergic stimuli may increase the risks of general anesthesia and surgery.

Side effects

Metoprolol is generally well tolerated. Side effects include:

Possible serious adverse effects include:

Metoprolol can aggravate breathing difficulties in patients with asthma, chronic bronchitis, or emphysema.

What is the dosage for digoxin vs. metoprolol?

Digoxin

  • Digoxin may be taken with or without food.
  • Digoxin primarily is eliminated by the kidneys; therefore, the dose of digoxin should be reduced in patients with kidney dysfunction.
  • Digoxin blood levels are used for adjusting doses in order to avoid toxicity.
  • The usual starting dose is 0.0625-0.25 mg daily depending on age and kidney function.
  • The dose may be increased every two weeks to achieve the desired response.
  • The usual maintenance dose is 0.125 to 0.5 mg per day.

Metoprolol

  • Metoprolol should be taken before meals or at bedtime.
  • The dose for treating hypertension is 100-450 mg daily in single or divided doses.
  • Angina is treated with 100-400 mg daily in two divided doses.
  • Heart attack (acute myocardial infarction) is treated with three 5 mg injections administered 2 minutes apart followed by treatment with 50 mg oral metoprolol every 6 hours for 48 hours. After 48 hours, patients should receive 100 mg orally twice daily for at least 3 months.
  • The dose for congestive heart failure is 25 mg/daily initially. Then the dose is increased every 2 weeks to reach a target dose of 200 mg/daily orally.
  • Hyperthyroidism is treated with 25 to 30 mg by mouth every 6 hours.

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What drugs interact with digoxin and metoprolol?

Digoxin

Metoprolol

  • Calcium channel blockers and digoxin (Lanoxin) can lower blood pressure and heart rate to dangerous levels when administered together with metoprolol.
  • Metoprolol can mask the early warning symptoms of low blood sugar (hypoglycemia) and should be used with caution in patients receiving treatment for diabetes.
  • Fluoxetine (Prozac) can increase blood levels of metoprolol by reducing breakdown of metoprolol, and increase the side effects from metoprolol.

Are digoxin and metoprolol safe to use while pregnant or breastfeeding?

Digoxin

  • There are no adequate studies in pregnant women.
  • Digoxin is secreted in breast milk at concentrations similar to concentrations in the mother’s blood. However, the total amount of digoxin that will be absorbed from breast milk by the infant may not be enough to cause effects. Nursing mothers should use caution if they are taking digoxin.

Metoprolol

  • Safe use of metoprolol during pregnancy has not been established.
  • Small quantities of metoprolol are excreted in breast milk and may potentially cause adverse effects in the infant.

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Summary

Digoxin is used for treating adults with mild to moderate congestive heart failure and for treating abnormal heart rhythms. Digoxin is also used for increasing myocardial contractility in pediatric patients with heart failure. Metoprolol is used to treat high blood pressure, congestive heart failure, heart pain, hyperthyroidism, and some neurologic conditions. Metoprolol is used off-label to prevent migraine headaches.

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Medically Reviewed on 8/1/2019
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