Taking soluble forms of aspirin, paracetamol, ibuprofen and vitamin C tablets are putting users at risk of an early death because they contain too much salt, a Scottish study claims.

Researchers said that using the soluble painkillers, which are commonly used to get rid of headaches, leads to a 22% higher chance of suffering a stroke and a 28% increased risk of dying prematurely. People regularly using the drugs are also seven times more likely to develop high blood pressure than those taking similar drugs that contain no salt.

Doctors at Dundee University and University College London collated data from almost 1.3 million patients who were given at least two prescriptions of salt-containing drugs, or who were taking the same drugs without salt over the long-term.

Those with the highest number of prescriptions, and doses, experienced the most negative impact on their health.

Lead researcher Dr Jacob George, senior lecturer in Clinical Pharmacology at Dundee, warned GPs against prescribing such medications. He also called on medicine manufacturers to take greater responsibility in warning the public of their products' salt content.

He said: "There is clearly a risk associated with these medications. The data from this study will enable patients and their doctors to make an informed choice on whether they should start or continue these medications.

"Physicians should prescribe sodium-containing formulations with caution and only if there are compelling reasons to do so.

"Although we did not study non-prescription or over-the- counter medicines, we think it is reasonable to extrapolate our findings to these medicines."

He added that despite major efforts to reduce salt intake, the makers of the drugs do not have to comply with any legislation on the labelling of sodium-based medications.

Dr George said: "These drugs are also available over the counter; they can be picked up in the supermarket, and we have no control over how many millions of people are buying these drugs.

"The sodium content of medicines seems to be an important topic that needs to be dealt with by regulatory agencies.

"The public should be warned about the potential hazards of high sodium consumption in prescribed medicines, and these should be clearly labelled with the sodium content in the same way as foods are labelled."

High salt levels can be found in everyday medicines such as antacids, some cold and flu remedies, as well as dispersible painkillers.

The recommended maximum daily intake is six grammes per adult, which translates to about 2.4 grammes of sodium.

The use of soluble products are popular with those who struggle to take their medication in pill form.

However, the high-sodium content may leave the user sus­ceptible to serious health issues, such as high blood pressure and the possibility of stroke.

Professor Tom MacDonald, president of the British Hyper­tension Society, said the report was worrying, adding: "Avoiding possible causes, such as taking tablets with a high sodium content, could help to start reducing this awful disease."

Dr Madina Kara, neuroscientist at the Stroke Association, said: "It is crucial to be aware of our sodium intake because excess salt in our diet can lead to high blood pressure, which is the single biggest risk factor for stroke.

"A diet low in saturated salt and fat, regular exercise and blood pressure checks can go a long way to keeping your stroke risk down."