Metoprolol vs labetalol

Metoprolol vs labetalol

Metoprolol vs. Labetalol

Metoprolol is a beta-adrenergic blocking agent (beta-blocker) that treats high blood pressure (hypertension), angina, congestive heart failure, abnormal heart rhythms, hyperthyroidism, and some neurologic conditions. It also prevents migraine headaches.

Labetalol, another beta-blocker, is used to treat high blood pressure. It blocks adrenergic receptors on arteries, causing them to expand and lowering blood pressure.

Side effects of metoprolol and labetalol


Metoprolol may cause:

  • Abdominal cramps
  • Diarrhea
  • Constipation
  • Fatigue
  • Insomnia
  • Indigestion
  • Nausea
  • Depression
  • Dreaming
  • Memory loss
  • Fever
  • Impotence
  • Lightheadedness
  • Low blood pressure
  • Decreased exercise tolerance
  • Increased triglycerides
  • Bronchospasm
  • Cold extremities
  • Sore throat
  • Shortness of breath or wheezing

Serious adverse effects may include:

  • Slow heart rate
  • Raynaud’s phenomenon
  • Hepatitis
  • Increased insulin resistance

Metoprolol may worsen breathing difficulties in patients with asthma, chronic bronchitis, or emphysema.

WARNING: Metoprolol can cause dangerously slow heart rates and worsen heart failure symptoms in patients with existing heart conditions. Stopping metoprolol abruptly can worsen angina and occasionally cause heart attacks. High-dose metoprolol before non-cardiac surgery is associated with adverse effects. Consult a physician before discontinuing metoprolol.


The most common side effects of labetalol are:

Postural hypotension may occur rarely. Patients should be monitored within two to four hours of the initial dose and after any changes in dose.

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Other important side effects include:

  • Sexual dysfunction
  • Abnormal heart rhythm
  • Slow heart rate
  • Liver failure
  • Allergic reactions

Dosage of metoprolol vs. labetalol


  • Metoprolol should be taken before meals or at bedtime.
  • The dosage for hypertension is 100 to 450 mg daily in single or divided doses.
  • The dosage for angina is 100 to 400 mg daily in two divided doses.
  • The dosage for heart attack is three 5 mg injections administered 2 minutes apart, followed by 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 dosage for congestive heart failure is 25 mg daily initially, with gradual increases every 2 weeks to reach a target dose of 200 mg daily orally.
  • The dosage for hyperthyroidism is 25 to 30 mg by mouth every 6 hours.


  • The recommended starting oral dose of labetalol is 100 mg twice daily. The dose may be increased by 100 mg twice daily every 2 to 3 days based on blood pressure response. Usual maintenance doses are 200 to 400 mg twice daily. Patients with severely high blood pressure may require 1.2 to 2.4 g daily.
  • Side effects may be reduced with three daily doses of labetalol instead of two. Stopping or changing the dose of labetalol should be done under the guidance of a physician due to potential serious side effects. The initial intravenous dose is 20 mg injected over 2 minutes. Additional injections of 40 or 80 mg may be administered every 10 minutes as needed up to a total dose of 300 mg. Labetalol can also be given by intravenous infusion at a rate of 1 to 2 mg/minute.
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Drug interactions with metoprolol and labetalol


  • Calcium channel blockers and digoxin (Lanoxin) can dangerously lower blood pressure and heart rate when taken with metoprolol.
  • Metoprolol can mask the early warning symptoms of low blood sugar and should be used cautiously in patients with diabetes.
  • Fluoxetine (Prozac) can increase blood levels of metoprolol, intensifying its side effects.


  • Labetalol can mask early warning symptoms of hypoglycemia in diabetes patients, so blood sugar monitoring should be increased.
  • Combining labetalol with tricyclic antidepressants may increase tremors.
  • Adrenergic stimulating drugs used to treat asthma may have reduced effectiveness when combined with labetalol.
  • Glutethimide may decrease labetalol’s effectiveness.
  • Cimetidine may increase labetalol’s effectiveness.
  • Halothane anesthesia may contribute to the blood pressure lowering effects of labetalol.

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Safety of metoprolol and labetalol during pregnancy or breastfeeding


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


  • There are no adequate studies of labetalol during pregnancy.
  • Labetalol is excreted in human breast milk, and caution is advised for nursing mothers due to the risk of slow heart rate in infants.


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