Racing heart? When beta blockers are an alpha drug

Many drugs have invisible effects. The drug companies labour to confer personality through eye-catching shapes and colours, and unusual names, because the actual experience of taking the drug is so unexciting. This is particularly true of the medicines for chronic health problems: diabetic drugs, blood pressure tablets, statins.

Unless you’re unlucky enough to suffer side effects, nothing obvious happens when you take most pills – nothing to feel or see, no sudden change in your health. If you felt a bit tired and lousy before your 40mg of simvastatin, you’re likely to feel a bit tired and lousy after it, too. Since all the benefits lie in the longer term, the whole experience is basically abstract. This is why, as students, we used to find beta blockers exciting: at last, medication that clearly does something.

Patients on beta blockers were a reliable ward-round trick. The consultant would ask you to “assess this person’s pulse”. You’d step forward importantly, take the patient’s wrist and look up at the clock through narrowed eyes. Within seconds you’d realise the pulse was improbably slow: could this be true, or were you counting wrong? While you held on, hoping for an answer to declare itself, your fingers would start to sweat. “Are they bradycardic?” you’d try. “Am I psychic?” the consultant would respond, wittily. This ritual would be followed by a faltering attempt to recall the causes of a bradycardia – a pulse rate slower than 60 beats a minute – until someone remembered to look in the drug chart. “Bisoprolol!” she’d cry. “Jesus!” our consultant would say. “Finally!”

Beta blockers block the receptors that receive messages from stress hormones such as adrenalin. They therefore prevent adrenalin from doing its job of speeding up the heart rate ready for fight or flight. Released from this stimulation, the heart ticks along at its baseline rate of around 50 beats a minute.

The clinical applications of beta blockers are, for once, easy to work out from their physiological effects. They are used whenever slowing the heart rate may be beneficial. You can give them to block the physical effects of anxiety: by preventing the pounding sensation in your chest, they can provide short-term relief from performance nerves, phobias and panic attacks. They can work as prophylaxis for migraines (although we don’t know how). They were once regularly used to control blood pressure (but are no longer the recommended first-line treatment). But their most widespread use is probably to regulate the function of the heart itself, especially when it’s been damaged by a heart attack, years of high blood pressure, or a faulty valve. Here, the role of beta blockers is well-established. By lessening the amount the heart has to pump, they reduce its workload, so allowing it to have a bit of a rest.

And so beta blockers have gradually come to be part of the treatment for all kinds of coronary artery disease. For example, they are widely used even when the heart is not failing – many patients who have either had a heart attack, or are at high risk of one, get prophylactic beta blockers. But a recent study shows that there is unlikely to be any benefit. Although logically the drug seems as if it should be helpful (why not take the strain off a heart that might be damaged, or heading for damage?), in fact the research doesn’t back this up. Alongside their other effects, beta blockers can also cause fatigue, nightmares, impotence and cold feet. These are drugs that do things: you want to be sure you need them first.

Sophie Harrison is a hospital doctor in South Yorkshire

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