metoprolol

Metoprolol is a beta-blocker (beta-adrenergic blocking agent) used for the treatment of:

• High blood pressure
• Heart pain
• Congestive heart failure
• Hyperthyroidism
• Abnormal heart rhythms
• Some neurologic conditions.

Metoprolol's off-label use is to prevent migraine headaches.

• Metoprolol is used to treat:
  • High blood pressure (hypertension
  • Congestive heart failure
  • 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:
  • Preventing migraine headaches
  • Treatment of hyperthyroidism and certain types of tremors

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, 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 However, long-term therapy with metoprolol should not be routinely withdrawn before major surgery. The 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 diabetes treatment.
• Fluoxetine (Prozac) can increase blood levels of metoprolol by reducing the breakdown of metoprolol and increasing the side effects of 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.