Prescribing behaviour in general practice: the impact of promoting therapeutically equivalent cheaper medicines

The volume and cost of prescribing varies considerably between practices. This variation is at least in part due to the prescribing behaviour of individual doctors, who are often faced with a range of therapeutically equivalent generic and brand-name drugs.

To assess the impact on general practitioners' prescribing behaviour of promoting therapeutically equivalent lower cost prescribing in conjunction with an incentive scheme.

Annual prescribing data from before (1992-93) and after (1993-94) implementation of the incentive scheme were compared retrospectively for general practices in the former Northern Regional Health Authority. Main outcome measures were the practices' 1993-94 rates of prescribing relative to those in 1992-93 for 18 drugs prescribed by brand name, of which 10 were targeted in the promotion, and for 14 drugs or classes of drugs either with equivalent cheaper alternatives or of limited clinical value (10 targeted and four not).

For 17 of the 18 drugs, brand name prescribing rates were significantly lower in 1993-94. Reductions in rates were greater for the 10 drugs appearing in the scheme's promotional literature. For other cost-saving measures, total prescribing rates were lower for seven classes of drugs, unchanged for one, but higher for the other six, all of which had been targeted. According to the growth in their overall per capita prescribing costs between the two study years, the 499 practices were categorized as low, average or high. Overall costs and individual prescribing rates for the majority of drugs studied were similar for these three practice groups in 1992-93. In 1993-94, practices' changes in prescribing volume differed between the groups, with the lowest increases in the low cost-growth group for all but one of the 32 classes of drugs.

Generic substitution was more easily implemented than more complex hints regarding cost-saving substitutions. Practices with smaller overall cost growth were making greater use of cost-beneficial prescribing strategies, whether promoted or otherwise. Simple messages may improve the cost-effectiveness of prescribing in the UK. With information support and encouragement, many prescribers appear to have modified their prescribing habits.