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Salt and prescribing behaviour

How a little bit of salt as a visual aid helped to modify prescribing behaviour in Northumberland.

Aware of the benefits of reducing salt intake, the prescribing team at North Northumberland PCG decided to see if they could find ways to change the behaviour of clinicians and patients. They chose to use a visual aid (a small bottle of salt) coupled with relevant information. This case study describes the background to the work, the way the initiative was managed by the team, progress so far, and some of the lessons from the work.

What is the background to the initiative?

The level of salt consumption in the western world has risen over the past few decades partly through the increased use of processed foods. The Department of Health has given a reference value for the daily salt intake as 70mmol [1] (1.6g sodium, or approximately 4g sodium chloride per day). WHO recommended, in 1982, that daily salt consumption should be 5g or less [2].

For many years now it has been recognised that there are potentially significant clinical grounds for avoiding effervescent medicinal products containing high levels of sodium in almost all patients, and especially those with hypertension, coronary heart disease, oedema, and renal failure.

Evidence exists that reducing salt intake in elderly patients by 5g per day can significantly reduce blood pressure (BP) with an effect similar to the reductions in BP achieved in trials assessing treatment with a single anti-hypertensive [3]. Reduced sodium intake is an effective supplementary treatment in hypertension [4]. Eliminating the amount of sodium equivalent to just four effervescent co-codamol tablets daily could facilitate the withdrawal of one anti-hypertensive in these patients (30% reduction in the risk of relapse) [5]. In addition, effervescent preparations cost the NHS more in terms of acquisition costs and may substantially contribute to other opportunity costs due to worsening of disease or symptoms affecting hospital admission rates and quality of life.

How was the work tackled?

Because of the logistical problems associated with a large rural area, the team decided to test whether a postal intervention could change practice when the message was simple, contained a visual aid and was accompanied by peer pressure i.e. prescribing information was shared within the PCG in an open manner. Across the practices there are approximately:

2,500 patients with bendrofluazide,

1,800 patients with atenolol,

50-90 patients with a statin

Despite this focus on effervescent analgesics it was recognised that some patients, for example those with oesophageal motility problems, stricture or oesophageal cancer or other forms of terminal illness may find effervescent preparations easier to take. Moreover, a limited number of GPs in two of the practices had seen the demonstration bottle several months before this intervention.

The practical steps

During November 1999 all GPs, pharmacists and practice nurses in North Northumberland PCG were circulated with a bottle containing 8.8g of sodium chloride. The bottle was to be used as a practical demonstration, for patients and general practitioners, of how much sodium is present in eight tablets (one day's treatment) of effervescent co-codamol 8/500 and 30/500 and paracetamol (calculations were based on a figure of 427mg sodium per tablet). Many effervescent OTC analgesics contain similar levels of sodium. Accompanying the demonstration was a copy of the PCG prescribing update, which contained information on clinical implications of the sodium content of effervescent analgesics.

Attention was drawn briefly to the prescribing of effervescent analgesics during subsequent prescribing meetings by the PCG prescribing adviser, SPRG and where relevant a practice pharmacist during the study period in all the practices. The local trust was also informed of the intervention as some effervescent prescribing was initiated in secondary care either on the wards or in the Accident and Emergency department.

Did it make a difference?

Prescribing units were used to allow a simple comparison to be made between practices: limited resources allowed only a simple analysis of the results of the initiative. More sophisticated methods [7, 8] to compare prescribing are available but none are necessarily more relevant for such a specific area of prescribing and in any case the primary objective of the intervention was to reduce prescribing volume. Nor have the team, for similar reasons, compared prescribing with a control PCG.

PACT data was analysed to assess changes in prescribing volume after the intervention. Total number of tablets prescribed was used as a measure of volume. Daily divided doses were not used, as all the drugs in question have the same dose. Dividing the total number of tablets prescribed by the practices patient units compared practices individual prescribing rates. Although this was unnecessary to measure reductions in prescribing volume, it did allow practices to compare their prescribing rates with other practices. These data have limitations in that they do not allow the analysis of how many patients were affected, or whether prescribing was altered for patients with CHD or not.

Detailed results

Prescribing in May 1999 was compared with May 2000. This gives the year on year change; and minimises the impact of any seasonal variation in prescribing.

Table 1 shows that prescribing of effervescent analgesics within the PCG, in terms of the total number of tablets prescribed, was reduced by 31% (from 62,774 to 43,710) between May 1999 and May 2000. The trend for the PCG between April 1999 and May 2000 showed a sustained reduction in prescribing since February 2000.

Table 2 shows that prescribing of effervescent analgesics (total number of tablets prescribed) was reduced in ten out of the eleven practices within the PCG. The largest reduction was 92% for practice 8. One practice (practice 5) had an increase in prescribing of 85%, but this was from a very low baseline of 230 tablets per month and most likely reflected a normal variation in prescription issue.

What has been learnt?

The postal intervention appears to have been successful in this instance and certainly was quicker and less labour intensive than a more conventional approach to influencing change in prescribing. Which aspects of the intervention led to success is less clear, although it is likely to have been a combination of all of the elements.

Sending out the information by post to everyone at once allowed professionals to co-operate and gave some momentum to change. However passive dissemination of information has been shown to have a poor record in effecting change [6].

There was an element of outreach , although the time spent during practice visits on effervescent analgesics was minimal (simply asking if the salt bottle was useful) and was not the main purpose of the meeting. Including the salt demonstration may have effectively targeted one of the barriers to change and helped draw attention to the message in the prescribing update.

Giving practices comparative prescribing data may also have contributed to the success. Because the data was not anonymous it allowed the potential for practices to compare their performance and may have introduced an element of competition.

How did practices respond?

Practices used a variety of different methods of implementation including opportunistic changes and more systematic approaches.

One practice had a well-established and simple form of internal peer review. This involved the circulation of a list of patients on a particular medicine, (naming the prescribing GP) amongst all partners. This was a very efficient way of effecting this change at practice level.

Making the salt bottle available at the point where medication is handed to patients may have been helpful in managing patients' expectations as this is often the point at which patients first notice the change to their medication. One practice kept a bottle of salt at the reception desk and attributed their success in changing prescribing partly to this.

Action by Pharmacists

One pharmacy in the PCG provided point of sale (EPOS) data, which showed a halving of the sales of generic effervescent co-codamol by intervening with the salt bottle during purchases. Patients were not generally refused sales but were persuaded to choose capsules or tablets instead.

How did patients react?

One factor, which seemed important in persuading patients to change, was their basic belief in the harmfulness of salt. In order to be successful at this level the patient needed to accept that excess salt in the diet was harmful to them, and that 8.8g constituted an excessive amount. A small minority of patients believed either that this extra amount of salt was beneficial, or did not believe that they would be harmed by it. One patient said his life would end if he didn't get his effervescent co-codamol!

Will the changes last: a lasting effect?

The team estimate that from this short time-period across North Northumberland patients formerly on effervescent analgesics are now collectively consuming 252kg less sodium chloride per year. Also approximately £9,000 worth of future annual prescribing resources has been released which will allow the treatment of an extra 962 patients with atenolol 50mg (based on DT price for December 2000).

Will this change be sustained? The outcomes listed here were circulated in the form of a prescribing update in September 2000 to all those on the original circulation list in order to complete the audit cycle and encourage further reductions in prescribing.

For more information contact

Steve Gray, Prescribing Adviser
North Northumberland PCG
The Bondgate Surgery, Infirmary Close
Alnwick NE66 2NL
Telephone 01665 626724
Fax 01665 626774 Email


1. Martindale 29th edition, The Pharmaceutical Press. 1989, 1023

2. Martindale 31st edition, The Pharmaceutical Press. 1996, 1184

3. Cappuccio FP; Markandu ND; Carney C; Sagnella GA; MacGregor GA. Double blind trial of salt restriction in older people. Lancet 1997; 350: 850-854

4. Graudal NA; Galle AM; Garred P. Effects of sodium restriction on blood pressure, renin, aldosterone, catecholamines, cholesterols and triglycerides: a meta-analysis. JAMA 1998; 279(17): 1383-1391

5. Whelton PK; Appel LJ; Espeland MA; Applegate WB; Ettinger WH Jr; Kostis JB; Kumanyika S; Lacy CR; Johnson KC; Folmar S; Cutler JA. Sodium restriction and weight loss in the treatment of hypertension in older persons. JAMA 1998; 297(11): 839-846

6. Getting evidence into practice. Effective Healthcare 5(1) February 1999

7. National Prescribing Centre.

8. D C E F Lloyd, C M Harris, D J Roberts, Specific therapeutic group age-sex weightings related prescribing units (STAR-PUs): weightings for analysing general practices' prescribing in England BMJ 1995, 311, 991-994