Metoprolol vs. labetalol: What’s the difference?
- Metoprolol and labetalol are beta-blockers (beta-adrenergic blocking agents) used to treat high blood pressure (hypertension).
- Metoprolol is also used to treat heart pain (angina), congestive heart failure, hyperthyroidism, abnormal heart rhythms, and some neurologic conditions, and to prevent migraine headaches.
- Brand names for metoprolol include Lopressor and Toprol XL.
- Side effects of metoprolol and labetalol that are similar include diarrhea, fatigue, nausea, sexual dysfunction/impotence, and shortness of breath.
- Side effects of metoprolol that are different from labetalol include abdominal cramps, constipation, insomnia, indigestion, depression, dreaming, memory loss, fever, lightheadedness, low blood pressure, decreased exercise tolerance, increased triglycerides, bronchospasm, cold extremities, sore throat, or wheezing.
- Side effects of labetalol that are different from metoprolol include dizziness, headache, fluid retention (edema), abnormal heart rhythm, and slow heart rate.
What are metoprolol and labetalol?
Metoprolol is a beta-adrenergic blocking agent (beta-blocker) that blocks the action of the sympathetic nervous system (a portion of the involuntary nervous system) and is used to treat high blood pressure (hypertension), heart pain (angina), congestive heart failure, abnormal heart rhythms, hyperthyroidism, and some neurologic conditions. Metoprolol also is used to prevent migraine headaches.
Labetalol is a beta-blocker used to treat high blood pressure. Nerves from the adrenergic nervous system travel from the spinal cord to arteries where they release norepinephrine. Norepinephrine attaches to adrenergic receptors on arteries and causes the arteries to contract, narrowing the arteries, and increasing blood pressure. Labetalol blocks receptors of the adrenergic nervous system. When labetalol attaches to and blocks the receptors, arteries expand, resulting in a fall in blood pressure.
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What are the side effects of metoprolol and labetalol?
Metoprolol
Metoprolol is generally well tolerated. Side effects include:
- 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
Possible serious adverse effects include:
- Slow heart rate
- Raynaud's phenomenon
- Hepatitis
- Increased insulin resistance
Metoprolol can aggravate breathing difficulties in patients with asthma, chronic bronchitis, or emphysema.
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.
Labetalol
The most common side effects of labetalol are:
Postural hypotension (a rapid decrease in blood pressure when going from the lying or seated position to the standing position that may cause lightheadedness or fainting) occurs rarely. Patients should be observed for this possible side effect within two to four hours of the first labetalol dose and after any changes in dose.
Other important side effects include:
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What is the dosage of metoprolol vs. labetalol?
Metoprolol
- Metoprolol should be taken before meals or at bedtime.
- The dose for treating hypertension is 100 to 450 mg daily in single or divided doses.
- Angina is treated with 100 to 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.
Labetalol
- The recommended starting oral dose of labetalol is 100 mg twice daily and the dose can be increased by 100 mg twice daily every 2 to 3 days based on the response of the blood pressure. 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 less if labetalol is given in three daily doses rather than two. Stopping or changing the dose of the drug should be directed by a physician because serious side effects may occur. The initial intravenous dose of labetalol 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 also may be administered by intravenous infusion at 1 to 2 mg/minute.
What drugs interact with metoprolol and labetalol?
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.
Labetalol
- Labetalol can mask early warning symptoms of hypoglycemia (low blood sugar) such as tremors and increased heart rate, which are the result of activation of the adrenergic nervous system. Therefore, people with diabetes taking medications that lower blood sugar such as insulin or oral antidiabetic medications may need to increase the frequency with which they monitor their blood sugar in order to prevent hypoglycemia.
- Combining labetalol with tricyclic antidepressants such as amitriptyline (Elavil, Endep), imipramine (Tofranil), or nortriptyline (Pamelor) may lead to an increase in tremor which is a side effect of tricyclic antidepressants.
- If combined with adrenergic stimulating drugs used for treating asthma, for example, albuterol (Proventil, Ventolin) or pirbuterol (Maxair), the adrenergic blocking effects of labetalol may counteract the effects of the stimulating drugs and reduce their effectiveness for treating asthmatic attacks. More of the adrenergic drug may be needed.
- Glutethimide (Doriden) may decrease the effectiveness of labetalol by increasing its elimination. When both drugs are used together, more labetalol or less glutethimide may be needed.
- Cimetidine (Tagamet) may increase the effectiveness of labetalol by blocking its elimination and increasing its levels in the blood. Therefore, less labetalol may be needed when cimetidine and labetalol are used together.
- Halothane anesthesia may contribute to the blood pressure lowering effects of labetalol.
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Are metoprolol and labetalol safe to use while pregnant or breastfeeding?
Metopralol
- 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.
Labetalol
- There are no adequate studies of labetalol during pregnancy.
- Labetalol is excreted in human breast milk. Therefore, nursing mothers should use it cautiously because of the risk that the infant may develop a slow heart rate.