Beta blockers

They work by reducing heart muscle oxygen demand as the heart rate is slowed down. There are numerous beta-blockers on the market, but the following three are recommended for use, as they appear to meet nearly all clinical needs.

• Atenolol (Trade name Tenormin) (50-100 mg per day)
• Metoprolol (Betaloc, Lopresor) (100-200 mg per day)
• Propanolol (Inderal) (40 mg twice or 3 times a day)

Contra-indications to Beta blockers

Absolute

Beta-blockers should not be used in asthma, as they increase spasm of the bronchial tubes; nor in peripheral vascular disease, as circulation in the extremities (hands and feet) is reduced and the limbs are very painful as a result.

Verapamil (calcium-channel blockers) should not be used with a beta-blocker, as this can cause heart failure.

Relative

Careful consideration should be made before the use of beta blockers in diabetics, as beta blockers have the effect of raising blood sugar levels and the effect of low blood sugar can be masked, hence an increased risk of hypoglycaemia.

Beta-blockers should not be stopped suddenly, as this can worsen the angina.

Side effects

• Cold extremities
• Fatigue
• Bad dreams, but sleep disturbances are less common with Atenolol.