Metoprolol, first introduced in 1975, is one of a class of drugs known as beta-blockers. Beta-blockers are widely prescribed to treat disorders of the heart and circulation.

They work by blocking the action of adrenaline (epinephrine) and noradrenaline (norepinephrine) - two chemicals produced by the body that increase heart rate and raise blood pressure.

Cardioselective beta-blockers are especially effective at slowing heart rate and reducing the force of the heartbeat, thereby reducing the workload of the heart.

These actions make beta-blockers, including metoprolol, particularly effective in the treatment of a range of cardiovascular problems.

Metoprolol can be prescribed for:

• high blood pressure
• angina (the condition caused by narrowing of the arteries and reduction in the amount of oxygen-carrying blood reaching the heart).
• patients who have had a heart attack
• heart failure (a condition arising from weakening of the heart muscle which makes the heart pump less efficiently)
• certain disturbances of cardiac rhythm (arrhythmias)
• disorders of the function of the heart involving palpitations

It is also prescribed to help prevent migraine.

There are three main patient groups that metoprolol is particularly suited to benefit:

• patients with high blood pressure (primary prevention)
• patients who have had a heart attack (secondary prevention)
• patients with heart failure (secondary prevention)

It is normally taken as a tablet once or twice a day, but it can be given intravenously if rapid beta-blockade is required. Extended release (long-acting) metoprolol is also available for once daily oral treatment.

It can be used intravenously for the emergency treatment of heart attacks and arrhythmias. Around two dozen clinical trials have investigated its use in acute MI, and current guidelines advise prompt use unless there are contraindications. However, its value remains uncertain especially in the presence of current standard therapy and its use is limited. COMMIT/CCS-2 was designed specifically to assess its effectiveness in cutting deaths and reducing the risk of repeat heart attacks, because of this ongoing uncertainty.