Research Impact


Highlighting the health issues of high-sodium medicines

Research by UCL and the University of Dundee revealed long-term health risks of sodium-containing medications, including stroke and heart attack, leading to changes in labelling and prescriptions.

Non-Proprietary Medicine Prescription Bottle and Spilled Pills

28 April 2022

Sodium is essential to human health, but high levels of it can cause a range of problems in the body such as hypertension, cardiovascular disease and stroke. Current NHS guidelines recommend a maximum daily salt intake of 6g/day (equivalent to 2.4g or 104mmol sodium) for adults; patients with diagnosed conditions such as hypertension are also routinely recommended to reduce their intake.  

While the dangers of excess sodium due to high-salt foods have been known for a long time, research by Professor Li Wei (UCL School of Pharmacy) and her collaborators at the University of Dundee highlighted that medications may also play an important role in increasing sodium intake. This is a particular issue with formulations associated with rapid dispersion in water (effervescent, dispersible and soluble) which may contain additional sodium. For example, a single dispersible tablet of paracetamol may contain 18.6mmol sodium, and moderate repeat daily dosing may contribute significantly to someone’s daily sodium intake. 

A significantly increased risk of cardiovascular problems 

Professor Wei’s study compared the records of 61,072 patients taking high-sodium medications who had experienced a cardiovascular event (such as a heart attack or stroke) with a control group.  

The study reported a 16% increase in non-fatal heart attacks, non-fatal strokes or vascular death, a seven-fold increase in the risk of developing hypertension, a 22% increase in risk of incident stroke and a 28% increase in all-cause mortality in patients who were prescribed sodium content versions of the selected medications compared to matched patients taking the same medications in non-effervescent, soluble or dispersible forms.  

The risk of a cardiovascular event increased with higher medication intake. The authors concluded that the use of high sodium-content formulations was associated with significantly increased chances of cardiovascular problems.  

Compulsory labelling for high-sodium medicines 

At the time Professor Wei’s study was conducted (2013), sodium content and labelling was regulated for foods but there was no such requirement for medications. The Director of Vigilance and Risk Management of Medicines at the UK’s Medicines and Healthcare Products Regulatory Agency used Professor Wei’s results to write about the effects of excess dietary sodium to the EMA (European Medicines Agency). This has in turn led to the publication of European-wide guidance on the relabelling of medicines. 

It is now compulsory for medicines with a sodium content in excess of > 1mmol (23mg) per dose to be labelled both as mg per dose and as a percentage of the recommended daily dietary intake of sodium for an adult; this is stated in the in-package Patient Information Leaflet (PIL) and Summary of Product Characteristics (SPC).  

Increasing awareness among doctors and the public 

The EMA guidance also requires doctors to take medications into account when prescribing a low-sodium diet. Effervescent medical supplements and painkillers have also been highlighted as a high source of sodium intake in the NHS salt guidelines as part of the broader UK government Eat Well campaign. 

Follow up studies have shown that there has subsequently been a significant decrease in the prescription of high sodium containing medications since guidance was changed. Prescription levels of these medications decreased from 1089/10,000 to 841/10,000 members of the UK population, while there was also a corresponding 4.5-fold rise in the annual rate of decrease of prescriptions for high sodium medications. 

Research synopsis

Changing international guidance on sodium-containing medications to improve heart health 

Sodium is essential to human health, but high levels of it can cause a range of problems in the body such as high blood pressure and heart disease. While the dangers of excess sodium due to high-salt foods have been known for a long time, joint research by UCL and the University of Dundee was the first to identify the health problems caused by long-term sodium consumption in medications. This led to a European Medicines Agency (EMA) directive to ensure that the sodium content in medications is clearly labelled, leading to a big reduction in high-sodium medication prescriptions in the UK.