Metoprolol vs. atenolol: What’s the difference?
- Metoprolol and atenolol are beta-blockers used to treat high blood pressure (hypertension), heart pain (angina), congestive heart failure, hyperthyroidism, abnormal heart rhythms, and some neurologic conditions.
- Metoprolol is also used to prevent migraine headaches.
- Brand names for metoprolol include Lopressor and Toprol XL.
- A brand name for atenolol is Tenormin.
- Side effects of metoprolol and atenolol that are similar include abdominal cramps, diarrhea, constipation, fatigue, insomnia, nausea, depression, dreaming, memory loss, fever, impotence, lightheadedness, low blood pressure, cold extremities, and sore throat.
- Side effects of metoprolol that are different from atenolol include indigestion, decreased exercise tolerance, increased triglycerides, bronchospasm, shortness of breath, or wheezing.
- Side effects of atenolol that are different from metoprolol include slow heart rate, abnormal heart rhythm, numbness, and tingling.
What are metoprolol and atenolol?
Metoprolol is a beta-blocker (beta-adrenergic blocking agent), which 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, hyperthyroidism, abnormal heart rhythms, and some neurologic conditions. Metoprolol is also used to prevent migraine headaches.
Atenolol is a beta-blocker that blocks the effects of adrenergic chemicals such as adrenaline or epinephrine, which are released by nerves of the sympathetic nervous system. The beta-adrenergic nerves stimulate the heart muscle to beat more rapidly. By blocking the stimulation by these nerves, atenolol reduces the heart rate and is used to treat abnormally rapid heart rhythms. Atenolol also reduces the force of contraction of heart muscle and lowers blood pressure. By reducing the heart rate, the force of muscle contraction, and the blood pressure against which the heart must pump, atenolol reduces the work of heart muscle and the need of the muscle for oxygen, which helps in treating angina.
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What are the side effects of metoprolol and atenolol?
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.
Atenolol
Atenolol is generally well tolerated, and side effects are mild and transient. Its side effects include:
- Abdominal cramps
- Diarrhea
- Constipation
- Fatigue
- Insomnia
- Nausea
- Depression
- Dreaming
- Memory loss
- Fever
- Impotence
- Lightheadedness
- Slow heart rate
- Abnormal heart rhythm
- Low blood pressure
- Numbness
- Tingling
- Cold extremities
- Sore throat
Atenolol can cause breathing difficulties in patients with asthma, chronic bronchitis, or emphysema. In patients with existing slow heart rates (bradycardias) and heart blocks (defects in the electrical conduction of the heart), atenolol can cause dangerously slow heart rates and even shock. Atenolol reduces the force of heart muscle contraction and can aggravate symptoms of heart failure.
In patients with coronary artery disease, abruptly stopping atenolol can suddenly worsen angina, and occasionally precipitate heart attacks. If it is necessary to discontinue atenolol, its dosage can be reduced gradually over several weeks.
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What is the dosage of metoprolol vs. atenolol?
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.
Atenolol
- The dose for treating high blood pressure or angina is 25 to 100 mg once daily.
- Acute myocardial infarction (heart attack) is treated with two 5 mg injections administered 10 minutes apart. Ten minutes after the last injection, give 50 mg every 12 hours followed by 100 mg oral atenolol daily for 6 to 9 days. If atenolol injections are not appropriate, patients may be treated with 100 mg daily of oral atenolol for 7 days.
What drugs interact with metoprolol and atenolol?
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.
Atenolol
- Calcium channel blockers (CCBs) and digoxin (Lanoxin) can cause lowering of blood pressure and heart rate to dangerous levels when administered together with atenolol.
- Atenolol can mask the early warning symptoms of low blood sugar (hypoglycemia), and should be used with caution in patients receiving treatment for diabetes.
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Are metoprolol and atenolol safe to use while pregnant 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 cause adverse effects in the infant.