TENORMIN 50MG TABLETS

Indications

• Hypertension
• Angina pectoris
• Myocardial infarction (secondary prevention)
• Tachyarrhythmias

Dosage

Children: Refer to the BNF for Children for specific dosing information in paediatric patients.

Adults: The usual starting dose for hypertension is 50 mg once daily, which may be adjusted based on blood pressure response. For angina, the starting dose is also commonly 50 mg once daily, with adjustments as necessary.

Mechanism of action

Atenolol works by selectively blocking beta-1 adrenergic receptors located primarily in the heart. This action inhibits the effects of catecholamines (such as adrenaline) on these receptors, resulting in decreased heart rate, reduced force of contraction, and lowered blood pressure. This mechanism helps in controlling heart rate during stress or exercise and is beneficial in conditions like hypertension and angina.

Pharmacodynamics

The pharmacodynamics of atenolol involve its ability to decrease heart rate (negative chronotropic effect), reduce myocardial contractility (negative inotropic effect), and lower blood pressure. The onset of action typically occurs within 1 to 2 hours after oral administration, with peak effects seen within 2 to 4 hours. The duration of action is approximately 24 hours, allowing for once-daily dosing.

Pharmacokinetics

Atenolol is well absorbed following oral administration, with a bioavailability of approximately 50-60%. It has a volume of distribution of about 3-4 L/kg and is primarily eliminated through renal excretion as unchanged drug. The elimination half-life of atenolol is around 6-9 hours, but this may be prolonged in patients with renal impairment. Atenolol does not undergo significant hepatic metabolism, making it a preferred choice in patients with liver disease.

Contra-indications

• Severe bradycardia
• Heart block greater than first degree
• Cardiogenic shock
• Uncontrolled heart failure
• Sick sinus syndrome
• Hypersensitivity to atenolol or any component of the formulation

Adverse effects

• Fatigue
• Dizziness
• Hypotension
• Bradycardia
• Cold extremities
• Gastrointestinal disturbances
• Sleep disturbances
• Depression

Interactions

• Propafenone: Moderate (increases risk of cardiovascular adverse effects)

Precautions

• Use with caution in patients with asthma or a history of bronchospasm
• Monitor renal function, particularly in elderly patients
• May mask signs of hypoglycemia in diabetic patients
• Caution in patients with peripheral vascular disease

Pregnancy

Atenolol is generally considered to be contraindicated during pregnancy, especially in the third trimester, as it may cause fetal bradycardia and intrauterine growth restriction.

Breast-feeding

Atenolol is excreted in breast milk, and caution is advised when administering to breastfeeding mothers due to potential effects on the nursing infant.

Storage

Store at room temperature, away from moisture and heat. Keep the medication in its original container, tightly closed.

Formulations

• Tablets: 25 mg, 50 mg, 100 mg
• Oral solution: 5 mg/mL