• Metoprolol is a beta-adrenergic blocking agent that is used for treating high blood pressure, heart pain, abnormal rhythms of the heart, and some neurologic conditions. Examples of beta-adrenergic blockers include propanolol (Inderal, Inderal LA, Innopran XL), atenolol (Tenormin), and timolol (Blocadren).

• Lopressor and Toprol XL are brand names available for metoprolol in the US.

Yes

Yes

• Metoprolol is prescribed for patients with high blood pressure (hypertension).
• It also is used to treat congestive heart failure and angina pectoris (heart pain) related to coronary artery disease.
• Metoprolol also is useful in slowing and regulating certain types of abnormally rapid heart rates (tachycardias).
• Other uses for metoprolol include the
  • prevention of migraine headache,
  • hyperthyroidism, and
  • the treatment of certain types of tremors (familial or hereditary essential tremors).

Metoprolol is generally well tolerated. Side effects include

• abdominal cramps,
• diarrhea,
• constipation,
• fatigue,
• insomnia,
• nausea,
• depression,
• dreaming,
• memory loss,
• fever,
• impotence,
• lightheadedness,
• low blood pressure,
• cold extremities,
• sore throat, and
• shortness of breath or wheezing.

Possible serious adverse effects include

• slow heart rate,
• Raynaud's phenomenon,
• hepatitis, and
• 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 However, long-term therapy with metoprolol should not be routinely withdrawn prior to major surgery.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.

• 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.

• 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 metopropol by reducing breakdown of metoprolol, and increase the side effects from 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.

What preparations of metoprolol (Lopressor, Toprol XL) are available?

• Tablets: 25, 50, and 100 mg.
• Tablets (extended release): 25, 50, 100, and 200 mg.
• Injection: 1 mg/ml

How should I keep metoprolol (Lopressor, Toprol XL) stored?

• Tablets should be stored between 15 C and 30 C (59 F and 86 F).
• They should be protected from moisture and dispensed in tight, light-resistant containers.

How does metoprolol (Lopressor, Toprol XL) work?

• Metoprolol blocks the action of the sympathetic nervous system, a portion of the involuntary nervous system, by blocking beta receptors on sympathetic nerves. Since the sympathetic nervous system is responsible for increasing the rate with which the heart beats, by blocking the action of these nerves metoprolol reduces the heart rate and is useful in treating abnormally rapid heart rhythms.
• Metoprolol also reduces the force of contraction of heart muscle and thereby lowers blood pressure. By reducing the heart rate and the force of muscle contraction, metoprolol reduces the need for oxygen by heart muscle. Since heart pain (angina pectoris) occurs when oxygen demand of the heart muscle exceeds the supply of oxygen, metoprolol, by reducing the demand for oxygen, is helpful in treating heart pain.

When was metoprolol approved by the FDA?

• The FDA approved metoprolol in August 1978.