Metoprolol Drug Profile

What is Metoprolol?

Metoprolol is a prescription medication belonging to a class of drugs called beta-blockers, specifically beta-1 selective blockers. It is primarily used to treat high blood pressure, chest pain (angina), and heart failure, and to improve survival after a heart attack. This medication works by blocking certain stress hormones from affecting the heart and blood vessels.

Uses

Metoprolol has several FDA-approved medical uses:

• High blood pressure (hypertension): Helps lower blood pressure by reducing the heart’s workload and relaxing blood vessels
• Angina pectoris: Reduces chest pain episodes by decreasing the heart’s oxygen demand during physical activity or stress
• Heart failure: Improves heart function and reduces hospitalizations in patients with chronic heart failure when used alongside other heart failure medications
• Post-heart attack treatment: Reduces the risk of death and subsequent heart attacks when started within days of a heart attack
• Abnormal heart rhythms: Sometimes prescribed off-label to help control certain types of irregular heartbeats

How it works

Metoprolol works by selectively blocking beta-1 receptors in the heart, which are normally activated by stress hormones like adrenaline and noradrenaline. By blocking these receptors, metoprolol reduces heart rate, decreases the force of heart contractions, and lowers blood pressure. This reduces the heart’s workload and oxygen requirements, making it particularly beneficial for people with heart conditions.

Side effects

Common side effects include:

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• Fatigue and weakness
• Dizziness or lightheadedness
• Slow heart rate (bradycardia)
• Cold hands and feet
• Digestive issues (nausea, diarrhea, constipation)
• Sleep disturbances or vivid dreams
• Shortness of breath during exercise
• Depression or mood changes

Serious side effects requiring immediate medical attention:

• Severe breathing difficulties or wheezing
• Signs of heart failure (swelling in legs/ankles, sudden weight gain)
• Extremely slow or irregular heartbeat
• Severe dizziness or fainting
• Chest pain or worsening angina symptoms

Warnings and precautions

• Asthma and COPD: Should be used with extreme caution in patients with respiratory conditions, as it may worsen breathing problems despite being beta-1 selective
• Diabetes: May mask symptoms of low blood sugar and can affect blood glucose control, requiring closer monitoring
• Sudden discontinuation: Should never be stopped abruptly as this can cause dangerous rebound effects including heart attack, especially in patients with coronary artery disease
• Pregnancy: Classified as pregnancy category C; should only be used when benefits outweigh potential risks to the fetus
• Kidney and liver function: Dosage adjustments may be necessary in patients with severe liver impairment, though kidney problems typically don’t require dose changes

Interactions

• Calcium channel blockers (verapamil, diltiazem): Can cause dangerously slow heart rate and low blood pressure when combined
• Digoxin: Metoprolol can increase digoxin levels, potentially leading to toxicity
• Insulin and diabetes medications: May enhance blood sugar-lowering effects and mask hypoglycemia symptoms
• NSAIDs (ibuprofen, naproxen): Can reduce metoprolol’s blood pressure-lowering effectiveness
• Antiarrhythmic drugs (amiodarone, propafenone): May increase risk of heart rhythm problems
• MAO inhibitors: Can cause severe interactions affecting blood pressure and heart rate
• Alcohol: May enhance the blood pressure-lowering effects and increase drowsiness
• Epinephrine (adrenaline): Beta-blockers can alter the body’s response to emergency epinephrine treatment

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Dosage

Metoprolol dosages vary significantly based on the condition being treated and whether the immediate-release or extended-release formulation is used. For high blood pressure, typical starting doses range from 25-100 mg twice daily for immediate-release tablets, or 25-100 mg once daily for extended-release formulations. Heart failure treatment usually begins with much lower doses (12.5-25 mg twice daily) and is gradually increased. Post-heart attack treatment may involve 25-50 mg twice daily, started within days of the event. All dosing should be individualized and carefully monitored by a healthcare provider, who will adjust the dose based on response and tolerance.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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