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Do formularies work?

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Comment

Formularies for medicines are used for quality control of care (antibiotics, parenteral feeding) and to reduce prescribing costs. There will always be good reasons why some pharmaceutical products should not be available, but what is the evidence that broader restrictions on availability have any effect on cost or care quality? Prompted by evidence from a randomised trial that patients switched antidepressants frequently ( Bandolier 95 ), a reader asked what evidence was there that formularies reduced cost, improved care, or both?

All other considerations being equal, an initial choice based on prescription costs is prudent, ethical, and clinically reasonable. Benefits at least in cost should follow this as night follows day. Bandolier expected a large literature and some good literature reviews. We found neither.

Search


PubMed was searched using the terms formulary and pharmacy together or separately, using limits of meta-analysis, review, and randomised controlled trial. Review articles and textbooks were also examined for relevant references. The aim was (in order) to find systematic reviews, reviews, or randomised trials looking at broader formulary restriction. When this strategy produced almost nothing of relevance, the search was repeated with prescribing and restriction.

Trial


One randomised trial [1] was found, that randomised physicians to prescribing a limited set of dosages of thyroxine. Thirty-three physicians prescribing thyroxine were randomised (open-label) by a computer to one of two formulary systems. One restricted thyroxine doses to 25, 50, 100, 125 and 150 μg, while the other had more dose strengths available (25, 50, 75, 100, 112, 125, 150, 175, 200, and 300 μg). Treatment efficacy was assessed by examination of thyroid function test results of patients prescribed thyroxine under the two systems, in patients taking thyroxine and newly prescribed for more than three months. Prescriptions were also analysed, and their cost calculated.

Results


Physicians in the restricted group were four years older than average, but otherwise there was no difference between the physicians in terms of clinical experience. There were 241 eligible patients. Thyroid function test results were the same (on average) for patients with similar conditions. Average doses prescribed were the same. Clinic visits were identical. Dose changes were the same. Prescriptions filled were the same. Cost was the same. Tablets prescribed were different (Figure 1).

Figure 1: Tablets dispensed per patient for each of thyroxine dosage form available



Comment


This was a successful experiment, in that it demonstrated that simplifying the doses of thyroxine available to prescribing physicians did not adversely affect patients, or increase costs. But then, 10 dose strengths for thyroxine seemed a bit excessive: MIMS has three.

This was a good trial which was conducted at the National Institutes of Health and various major sites in the USA. The trouble is that it does not prove that formulary restriction on a wider basis reduces costs or improves health outcomes. Indeed, what little Bandolier could find suggested the opposite.

One study [2] study provided empirical evidence of the influence of hospital formulary restrictions on pharmacy charges, all other hospital charges, and on length of stay, using a survey of hospital drug policies and hospital discharge data from Washington State in 1989. Some drug costs increased, others decreased, and some stayed the same. Across-the-board restrictions did not result in cost savings, although savings may be realized for particular drug categories. And a very recent review of using pharmacoeconomic influences [3] concluded that acquisition cost was the prime influence on formulary decisions, rather than overall healthcare costs and quality.

Where's the beef? Perhaps Bandolier has missed a huge literature of real importance. We'd love pharmacists and others who know this evidence to tell us where to find it, so that we can reprise this topic in a future issue.

References:

  1. KB Ain et al. Effects of restricting levothyroxine dosage strength availability. Pharmacotherapy 1996 16: 1103-1110.
  2. FA Sloan et al. Hospital drug formularies and use of hospital services. Med Care 1993 31 :851-67.
  3. DC Suh et al. Application of pharmacoeconomics to formulary decision making in managed care organizations. Am J Manag Care 2002 8:161-9.

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