Indications

Betaloc is indicated for the management of:

• Hypertension (high blood pressure).
• Angina pectoris.
• Cardiac arrhythmias, particularly supraventricular tachyarrhythmias.
• As an adjunct to the treatment of hyperthyroidism.
• Early intervention in acute myocardial infarction to reduce infarct size, prevent ventricular fibrillation, and reduce mortality.

Pharmacology

Metoprolol is a selective beta-1 blocker. It works by reducing or inhibiting the effects of catecholamines on the heart, which are released during physical and mental stress. This leads to a reduction in heart rate, cardiac output, cardiac contractility, and blood pressure. Metoprolol interferes less with insulin release and carbohydrate metabolism compared to non-selective beta-blockers and has a smaller effect on the cardiovascular response to hypoglycemia.

Dosage & Administration

The dosage and administration vary depending on the condition and formulation:

• Hypertension (Film-coated tablet): The total daily dose is 100-400 mg, given once or twice daily. The starting dose is 100 mg per day and can be increased by 100 mg weekly.
• Angina (Film-coated tablet): 50-100 mg two or three times daily.
• Arrhythmias (Film-coated tablet): 50 mg twice or three times daily. The dose can be increased up to 300 mg per day.
• Hyperthyroidism (Film-coated tablet): 50 mg four times a day, with the dose reduced as the patient becomes euthyroid.
• Myocardial Infarction (Film-coated tablet): Oral therapy starts 15 minutes after the last injection, with 50 mg every 6 hours for 48 hours. The usual maintenance dose is 200 mg daily in divided doses.
• Extended-release tablet:
  • Hypertension: 25 to 100 mg daily, in a single dose.
  • Angina Pectoris: The usual initial dose is 100 mg daily, in a single dose.
  • Heart Failure: The starting dose is 25 mg once daily for NYHA class II, or 12.5 mg once daily for more severe cases.
• IV Injection:
  • Arrhythmias: Up to 5 mg at a rate of 1-2 mg/minute, repeated if necessary, up to a total of 10-15 mg.
  • Myocardial Infarction: 5 mg every 2 minutes up to a maximum of 15 mg, followed by oral therapy.

Interaction

• Catecholamine-depleting drugs (e.g., reserpine, MAO inhibitors): May have an additive effect with beta-blockers.
• Drugs that inhibit CYP2D6 (e.g., quinidine, fluoxetine): Can increase Betaloc concentration, decreasing its cardioselectivity.
• Digitalis glycosides: Concomitant use can increase the risk of a slow heart rate (bradycardia).
• Clonidine: Beta-blockers may worsen the rebound hypertension that can occur after clonidine withdrawal.

Contraindications

Betaloc is contraindicated in patients with AV block, uncontrolled heart failure, severe bradycardia, sick-sinus syndrome, cardiogenic shock, and severe peripheral arterial disease. It is also contraindicated in cases of myocardial infarction complicated by significant bradycardia, first-degree heart block, low systolic blood pressure (<100mmHg), and/or severe heart failure.

Side Effects

Common side effects include tiredness, dizziness, depression, diarrhea, itching or rash, shortness of breath, slow heart rate, mental confusion, headache, and insomnia. Other reported effects are nausea, dry mouth, gastric pain, constipation, blurred vision, and decreased libido. It can also intensify AV block.

Pregnancy & Lactation

This is a Pregnancy Category C drug. There are no adequate studies in pregnant women. The drug should only be used during pregnancy if clearly needed. Metoprolol is excreted in breast milk in very small quantities, so caution should be exercised when administering it to a nursing woman.

Precautions & Warnings

• Bronchospastic Diseases: Use with caution in patients with bronchospastic diseases who do not respond to or cannot tolerate other treatments.
• Major Surgery: The need to withdraw beta-blocking therapy before surgery is debated, as it may increase the risks of anesthesia and surgical procedures.
• Diabetes and Hypoglycemia: Beta-blockers may mask the rapid heart rate associated with hypoglycemia.
• Peripheral Vascular Disease: Beta-blockers can precipitate or worsen symptoms of arterial insufficiency.
• Calcium Channel Blockers: Caution should be exercised when using with these agents due to potential effects on heart function and rhythm.

Use in Special Populations

• Hepatic Impairment: Use with caution.
• Pediatric Use: Safety and effectiveness have not been established in patients under 6 years of age.
• Geriatric Use: No significant differences in efficacy or side effects have been noted between older and younger patients.

Overdose Effects

An overdose can lead to severe low blood pressure, slow heart rate, heart block, heart failure, cardiogenic shock, cardiac arrest, bronchospasm, and coma. Symptoms typically appear within 20 minutes to 2 hours. Treatment involves monitoring cardiovascular, respiratory, and renal function, as well as blood glucose and electrolytes.

Therapeutic Class

Betaloc is a Beta-adrenoceptor blocking drug, or a beta-blocker.

Storage Conditions

Store in a cool and dry place, protected from light.