Development and evaluation of a primary care drug formulary
Aim This study asks if practices can collaborate to create a shared formulary, which influences prescribing. Secondary questions If so, how long does the effect last? To what degree can such a formulary influence volume of prescribing, choice of treatment and cost? Is there a limit to the number of practices involved before the effect is lost? Are doctors more influenced by the formulary if they are closely involved with its creation? Method Controlled trial in two stages. 100 general practitioners from 20 urban and semi-rural practices and 50 community nurses worked with a small team of facilitators to create a formulary. Between 1991 and 1999, prescribing by the participating doctors was compared with the prescribing by all other general practitioners in the county. Results Collaborative work resulted in a countywide formulary for primary care. The use of information to support prescribing changed from a few practices using their own formularies, to an evidence-based formulary supported by all five Primary Care Groups in the county. Choice of treatment changed in seven out of thirteen therapeutic groups. Volume of prescribing reduced in three groups. Cost reduced by F-3000 per doctor per annum. Conclusions Sharing resources between practices to create a primary care formulary can lead to modest changes in prescribing, sustained over three years, and lower overall costs. The largest observed changes were a 14% change in the choice of drugs for musculoskeletal conditions, and a saving of £5000 per practice per year on antibiotics. Such changes, attributed to the development of a formulary, also occur in practices that have no direct involvement, but later by several years. The greatest change in prescribing is seen immediately after a formulary is created and in those involved with its development. The funding for the work is estimated to amount to 17% of the saving on prescribing. Doctors and nurses from 32 practices can work together on such an intervention.