GPs have been advised to avoid prescribing effervescent, dispersible and soluble formulations of drugs after a study found they were associated with significantly increased risk of heart attacks and strokes – probably because of their high sodium content.
The study, published in the BMJ, followed more than one million patients for seven years and found patients prescribed sodium-containing formulations in primary care had a 16% higher risk of cardiovascular events compared with patients using standard preparations of the same drugs.
The increased risk was mainly due to an increase in strokes, probably as a result of an increased incidence of hypertension.
The drugs included sodium-containing preparations of paracetamol, ibuprofen, co-codamol, metoclopramide with aspirin and calcium carbonate and colecalciferol.
Researchers said taking just one of the drugs in sodium-containing form at the maximum dose can exceed a person’s recommended daily salt intake of 104 mmol/day. The average daily dose from sodium-containing drugs in the study was 106.8 mmol/day.
GP leaders said the findings served as a ‘timely reminder’ for GPs about the potential risks from high-salt preparations, but it was still too early to conclude a direct causal effect of the drugs in heart disease.
The research team, from Ninewells Hospital and Medical School in Dundee and University College London, studied 1,292,337 patients in the UK Clinical Practice Research Datalink database who received at least two prescriptions of sodium-containing formulations or matched standard formulations of the same drug between 1987 and 2010.
Over a mean of 7.2 years of follow-up, 61,072 patients had a CV event (non-fatal MI, nonfatal stroke or vascular death) and these were matched for age, gender and practice with the same number of control patients.
Those with CV events were more likely to be smokers and have a history of cardiovascular problems and other chronic disease than control patients, but after adjusting for confounders the researchers found a 16% increased odds of events associated with sodium-rich drugs. This was largely due to a 20% increased odds of stroke, which was probably associated with a seven-fold increase in the odds of hypertension among sodium-rich drug users.
The authors concluded: ‘Our results suggest that physicians should be prescribed sodium-containing formulations with caution and only if there are compelling reasons to do so.
‘Sodium loaded effervescent, soluble, or dispersible tablets should be avoided in patients at risk of hypertension, and patients prescribed these drugs should be carefully monitored for the emergence of hypertension.’
Dr Andrew Green, chair of the GPC prescribing subcommittee, said it made sense to warn patients about the potential risk from high-sodium medications.
He told Pulse: ‘We have been encouraging patients to reduce the quantity of sodium in their diet for a long time, so it would be illogical not to extend this stance from diet to medications. This study is interesting in that it quantifies the problem that we always suspected was there.
‘Effervescent and soluble formulations should only be prescribed when there is a reason to do so, accepting that there will be some patients for whom they aid compliance.’
He added: ‘Some years ago many medicines management teams encouraged the switching of patients to dispersible aspirin on the grounds of quite minor cost savings, and this serves as a timely reminder to GPs that in such circumstances they must take into account more than just the crude cost of the prescription.’