Prescribing Advice for GPs

An NHS Prescribing Advisers' Blog

Electrolytes and Diuretics

The British Journal of Clinical Pharmacology has published the results of a retrospective observational study into the effects of thiazide diuretics on electrolytes1. This study has also been reported by the BBC.

The study concludes that thiazides should be prescribed at low dose and the risk of electrolyte abnormalities should be managed by monitoring, especially in older patients.

Closer scrutiny of the study reveals that there are several confounders in the data. The data collected may not reflect current practice because it was time limited to a twelve year period between 1990 and 2002. Of the 32,000 patients identified detailed prescribing data was only available for 2942. Perhaps most importantly no details of co-morbidities or co-prescriptions were collected or analysed.

Current guidelines in Hypertension, like the NICE Guideline, recommend thiazides as first line drug. The Prescribing Formulary area of this site has made recommendations for first line drug choice that included a low dose thiazide.

Perhaps the only area of concern raised by this study is the finding that monitoring was not carried out in approximately two thirds of patients prescribed thiazides. The implementation of new contractual arrangements for GPs may have improved this recently but systematic monitoring is clearly an issue that still needs to be tackled.

Action: Media reporting of this publication may cause patients to report to their GP. Clinicians should be aware of the limitations of the study but take the opportunity to carry out routine monitoring, especially in those patients who are more prone to electrolyte abnormalities such as those prescribed other medicines and the elderly.


  1. Clayton JA et al. Thiazide diuretic prescription and electrolyte abnormalities in primary care. Br J Clin Pharmacol;61:87-95

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SMC reject Glucophage SR

The Scottish Medicines Consortium has rejected Sustained Release Metformin (Glucophage SR)® for the treatment of Type 2 Diabetes.

This drug was covered in Prescribing Bulletin 1 where it was recommended that clinicians continue to use the Immediate Release (IR) version of metformin where it is indicated.

Glucophage SR is claimed to have fewer gastrointestinal side effects. This claim is based upon data from observational studies. No differences in gastrointestinal side effects were noted in randomised clinical trials (RCT). RCTs are recognised occupying a higher level than observational studies in the hierarchy of evidence.

Action: Clinicians should continue to us IR Metformin as first line in the treatment of patients with Type 2 Diabetes.

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GP access to Prescribing Data

The Prescription Pricing Authority (PPA) has made electronic Prescribing & Financial Information for Practices (ePFIP) available to all GP Practices following the success of pilot started in 2003.

Practices must register to gain access to the system, registrations forms are available in Word or PDF format.

Once registered users can login to the system to access several prescribing reports including:

  • Practice Detailed Prescribing Information
  • Prescribing Analysis Report
  • Prescribing Review
  • Practice Prescribing Report
  • Prescribing Monitoring Document

The contents of each of these reports are described in detail on the PPA's ePFIP page.

Action: Paper copies of the above reports are no longer provided by the PPA. Practices are strongly urged to register for this system to allow them to monitor prescribing trends within the practice and in comparison to local and national trends.

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Pfizer defend Celecoxib

The Chief Medical Officer of Pfizer has written to the British Medical Journal (BMJ) following the publication of a study1 that failed to find consistent evidence of enhanced safety with any of the new cyclo-oxygenase-2 (COX-2) inhibitors compared with non-selective non-steroidal anti-inflammatory drugs (NSAIDs).

The letter claims that the conclusions drawn in the study (discussed previously) do not reflect the evidence. However this letter has produced many responses that have pointed out the flaws in Pfizer's response.

One of the key points raised is that much of the data is based upon observational studies. This kind of study occupies a lower level on the hierarchy of evidence than controlled trials.

The only controlled trial for celecoxib was the CLASS Study2. In this study there was no significant difference between celecoxib and ibuprofen and naproxen in the primary outcome of gastrointestinal ulcer complications.

Action: The NSAID debate seems set to run for some time. However, the evidence is clear that paracetamol carries a lower overall risk of cardiac, renal and gastrointestinal problems in clinical use.


  1. Hippisley-Cox et al. Risk of adverse gastrointestinal outcomes in patients taking cyclo-oxygenase-2 inhibitors or conventional non-steroidal anti-inflammatory drugs: population based nested case-control analysis. BMJ 2005;331:1310-1316
  2. Silverstein FE, Faich G, Goldstein JL, et al. Gastrointestinal toxicity with celecoxib vs nonsteroidal anti-inflammatory drugs for osteoarthritis and rheumatoid arthritis. The CLASS study: a randomized controlled trial. JAMA. 2000; 284:1247-1255

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InfoPOEM on Beta Blockers

An InfoPOEM has been produced that interprets the results and conclusions of the meta-analysis published in the Lancet titled "Should beta blockers remain the first choice in the treatment of primary hypertension?"1

The InfoPOEM is available online provided you have a subscription to InfoPOEMs.

The InfoPOEM concludes that, assuming the literature search for this study was adequate, beta-blockers are better than placebo but not other antihypertensives at preventing hypertension complications. It also points out that some patients will rightly need to be prescribed beta-blockers for co-morbidities like heart failure.

This site has already covered this study and suggested that clinicians should follow the NICE Guideline for Hypertension. Since this guideline places thiazides as first line the continued debate to those following this advice will seem irrelevant.

Action: Clinicians should follow the NICE Hypertension Guideline, which has placed thiazides as the first line treatment in hypertension. Beta-blockers still have a place in therapy as an add-on in primary hypertension and for patients with specific co-morbidities that benefit from beta-blocker therapy.


  1. Lindholm et al. Should beta blockers remain the first choice in the treatment of primary hypertension? A meta-analysis. Lancet 2005;366:1545-53

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