Metoprolol

A beta-1 selective blocker widely used for hypertension, angina, and heart failure.

What is Metoprolol?

Metoprolol is a cardioselective beta-1 adrenergic blocker used to manage hypertension, angina pectoris, heart failure, and arrhythmias.

It reduces heart rate, cardiac output, and myocardial oxygen demand.

History & Background

Metoprolol was developed to provide effective beta-blockade with fewer respiratory side effects compared to non-selective beta blockers.

Chemical Structure & Properties

• IUPAC name: (RS)-1-(isopropylamino)-3-[4-(2-methoxyethyl)phenoxy]propan-2-ol
• Molecular formula: C₁₅H₂₅NO₃
• Molar mass: 267.36 g/mol
• Functional groups: Secondary amine, ether, alcohol

Mechanism of Action

Metoprolol lowers blood pressure and heart workload by:

• Blocking β₁-adrenergic receptors in the heart
• Reducing heart rate and contractility
• Decreasing cardiac output

Pharmacokinetics

• Absorption: Well absorbed orally
• Peak plasma time: 1–2 hours
• Half-life: 3–7 hours
• Metabolism: Liver (CYP2D6)
• Excretion: Urine

Medical Uses

• Hypertension
• Angina pectoris
• Heart failure (extended-release form)
• Arrhythmias
• Post-myocardial infarction

Dosage Guidelines

Immediate-release: 50–100 mg/day in divided doses

Extended-release: 25–200 mg once daily

⚠️ Do not stop abruptly – taper gradually.

Side Effects

• Bradycardia
• Fatigue
• Dizziness
• Cold hands and feet

Warnings & Precautions

• May mask hypoglycemia symptoms
• Use caution in asthma and COPD
• Avoid sudden withdrawal

Drug Interactions

• Calcium channel blockers (verapamil, diltiazem)
• Antiarrhythmic drugs
• Insulin and oral antidiabetics

Frequently Asked Questions

Is metoprolol selective? – Yes (β₁ selective).

Is it used in heart failure? – Yes (ER form).

Does it lower heart rate? – Yes.

Is it safe long-term? – Yes, with monitoring.

⚠️ Educational content only. Not a substitute for professional medical advice.