Metoprolol: Uses, Dosage, Side Effects, and More
1. Drug Name
Generic Name: Metoprolol
Brand Name(s):
- Pakistan: Metolar, Metopress, Metolar XR
- India: Betaloc, Metolar, Starpress
- United States: Lopressor, Toprol-XL
- United Kingdom: Beloc, Metoprolol
2. Pharmacological Class
Class: Beta-blocker
Subclass: Selective beta-1 adrenergic receptor blocker
3. Mechanism of Action
Metoprolol selectively blocks beta-1 adrenergic receptors, primarily located in cardiac muscle, reducing the heart rate and cardiac output. This results in decreased blood pressure and reduced workload on the heart.
4. Indications
Primary Indications:
- Hypertension (high blood pressure)
- Angina (chest pain)
- Heart failure
- Myocardial infarction (heart attack) prevention and treatment
Off-label Uses:
- Migraine prophylaxis
- Essential tremor
- Anxiety and stage fright
5. Dosage and Administration
Standard Dosage:
- Hypertension: Initial dose of 25-100 mg once daily; usual maintenance dose of 100-450 mg daily.
- Angina Pectoris: Initial dose of 100 mg once daily; usual maintenance dose of 100-400 mg daily.
- Heart Failure: Initial dose of 12.5-25 mg once daily; usual maintenance dose of 100-200 mg daily.
Route of Administration: Oral (tablets or extended-release formulations).
Special Populations:
- Pediatric: Safety and efficacy not established in children.
- Geriatric: Lower initial doses recommended due to potential age-related decrease in renal function.
6. Pharmacokinetics
Absorption: Rapidly and completely absorbed from the gastrointestinal tract.
Distribution: Crosses the blood-brain barrier and placenta; distributed into breast milk.
Metabolism: Extensively metabolized in the liver.
Excretion: Primarily eliminated in the urine.
Half-life: 3-7 hours (short-acting), 24 hours (extended-release).
7. Contraindications
Metoprolol is contraindicated in patients who have a hypersensitivity to any component of the product, sinus bradycardia, heart block greater than first degree, cardiogenic shock, or overt cardiac failure.
8. Warnings and Precautions
Use with caution in patients with bronchospastic diseases, diabetes mellitus, or thyrotoxicosis. Abrupt withdrawal may exacerbate angina pectoris and precipitate myocardial infarction. Monitor for signs of heart failure exacerbation and hypotension.
9. Side Effects
Common Side Effects: Fatigue, dizziness, bradycardia, and cold extremities.
Serious Side Effects: Bradycardia, heart block, and worsening of heart failure. Discontinue use and notify a healthcare provider immediately if these occur.
10. Drug Interactions
Major Interactions: Verapamil, diltiazem, and amiodarone may increase metoprolol concentrations.
Moderate Interactions: Clonidine, digitalis, and NSAIDs.
Minor Interactions: Cimetidine, rifampin, and alcohol.
11. Pregnancy and Lactation
Pregnancy Category: Category C - Use during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Breastfeeding Considerations: Metoprolol is excreted into human milk. Discontinue nursing or the drug, taking into account the importance of the drug to the mother.
12. Patient Counseling Information
Key Points for Patients:
- Take metoprolol exactly as prescribed. Do not skip doses or stop taking the medication without consulting your healthcare provider.
- Avoid activities requiring mental alertness or coordination until drug effects are realized, as it may cause dizziness or fatigue.
- Monitor your blood pressure and heart rate regularly.
Administration Tips:
- Take metoprolol with a meal or immediately after a meal to enhance absorption.
- Do not crush, chew, or break extended-release tablets; swallow them whole.
- If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not