The many roles of beta blockers

Beta blockers are among the most versatile drugs in medicine. By blocking the effects of adrenaline on the body's beta receptors, they slow the heart, lower blood pressure and steady its rhythm - and the same basic action turns out to help a surprising range of conditions.

Their best-known roles are cardiac: treating high blood pressure, angina, heart failure and irregular heart rhythms such as atrial fibrillation, and protecting the heart after a heart attack.

Beyond the heart, beta blockers prevent migraine attacks, control the tremor of essential tremor, and ease the shaking and racing heart of hyperthyroidism. Taken before a stressful event, they blunt the physical symptoms of performance anxiety - the pounding heart and shaky hands - which is why musicians and public speakers sometimes use them.

They are not for everyone. Because they slow the heart and can narrow airways, they need care in people with asthma, very slow heart rates or certain circulation problems. Common side effects include fatigue, cold hands and vivid dreams.

Beta blockers should never be stopped abruptly after long use, since sudden withdrawal can trigger rebound high blood pressure, chest pain or even a heart attack. Any change belongs in a doctor's hands.