Researchers at the University of Dundee and University College London found that taking the maximum daily dose of some medicines would exceed the recommended daily limits for sodium, without any additional dietary intake.

They say the public “should be warned about the potential dangers of high sodium intake from prescribed medicines” and that sodium-containing formulations “should be prescribed with caution only if the perceived benefits outweigh the risks.”

They also call for the sodium content of medicines to be clearly labelled in same way as foods are labelled.

Numerous studies have shown that excess salt is harmful to heart health. Many commonly prescribed medicines have sodium added to improve their absorption into the body, but the effect of this is unknown.

The team, led by Dr Jacob George, Senior Clinical Lecturer and Honorary Consultant in Clinical Pharmacology at the University of Dundee, compared the risk of cardiovascular events (non-fatal heart attack, non-fatal stoke, or vascular death) in patients taking sodium-containing effervescent, dispersible and soluble medications with those taking non-sodium versions of the same drugs between 1987 and 2010.

Over 1.2 million UK patients were tracked for an average of just over seven years. During this time, over 61,000 incident cardiovascular events occurred.

Factors likely to affect the results, such as body mass index, smoking, alcohol intake, history of various chronic illnesses and use of certain other medications, were taken into account.

Overall, the researchers found that patients taking the sodium-containing effervescent, dispersible and soluble medications had a 16% increased risk of a heart attack, stroke or vascular death compared with other patients taking the non-sodium versions of those exact medications .

Patients taking the sodium-containing drugs were also seven times more likely to develop high blood pressure and overall death rates were also 28% higher in this group. These events are largely driven by an increased risk of hypertension and stroke.

The authors acknowledge that there is still some controversy regarding the relation between dietary sodium and cardiovascular events, but say their findings “are potentially of public health importance.”

They conclude: “Prescription of these sodium-containing formulations should be done with caution, and patients prescribed them should be closely monitored for the emergence of hypertension.”

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Emma Dickinson
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BMJ-British Medical Journal