Millions of patients worldwide taking effervescent, dispersible and soluble medicines have an increased risk of heart attacks and strokes because of the high salt content of such drugs, scientists said on Wednesday.
Researchers from Britain's University of Dundee and University College London found that with some "fizzy" versions of painkillers, vitamin supplements or other common medicines, taking the maximum daily dose would on its own exceed daily recommended limits for sodium, the main component of salt.
High salt intake has been linked to high blood pressure, or hypertension, which is a key risk factor for strokes, heart attacks and other cardiovascular diseases.
In a study published in the British Medical Journal (BMJ), they found that patients taking dispersible forms of drugs had a 16 percent increased risk of a heart attack, stroke or vascular death compared with patients taking the non-high-sodium versions of the same medications.
Jacob George, an honorary consultant in clinical pharmacology at Dundee who led the study, said patients, and consumers of over-the-counter medicines - such as soluble aspirin, effervescent vitamin C, or Bayer's Alka Seltzer for example - "should be warned about the potential dangers" of high sodium intake in medicines.
Doctors, he added, should be aware of the potential dangers and prescribe fizzy or soluble forms of drugs "with caution, only if the perceived benefits outweigh the risks".
"There are a lot of patients who need to use these formulations - those who have difficulty swallowing large tablets, for example," George said in a telephone interview. "But what we want is for patients to be able to make an informed decision with the help of their doctor."
Although there is some debate on the issue, many health experts believe that eating too much salt is bad for health and numerous studies have linked excess salt intake to high blood pressure, which can lead to strokes and heart attacks.
The World Health Organisation recommends a daily upper limit of sodium intake of less than 2 grams - equivalent to around 5 grams, or one teaspoon, of salt.
For this latest study, George's team tracked more than 1.2 million patients, comparing those taking sodium-containing effervescent, dispersible and soluble medicines with those taking non-sodium versions of the same drugs.
The study ran between 1987 and 2010 and patients were tracked for an average of just over seven years.
During this time, over 61,000 new so-called cardiovascular events - including heart attacks and strokes - occurred in the patients being studied.
Factors likely to affect the results, such as body mass index, smoking, alcohol intake, history of various chronic illnesses and use of other medicines, were taken into account.
Beside the 16 percent higher risk of a heart problem or stroke, the team also found patients taking sodium-containing drugs were seven times more likely to develop high blood pressure, and their overall death rate was 28 percent higher.
The researchers acknowledged that there is still some controversy about the link between dietary sodium and heart risks, but say their findings were anyway "potentially of public health importance".