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

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.

Labetalol

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.

Other important side effects include:

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

Dosage of metoprolol vs. labetalol

Metoprolol

• 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.

Labetalol

• 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.

Drug interactions with metoprolol and labetalol

Metoprolol

• 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

• 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

Metoprolol

• 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.

Labetalol

• 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.