Family Practice Vol. 18, No. 3, 333-338
© Oxford University Press 2001
Clincal Research |
Proton pump inhibitors: a study of GPs' prescribing
Department of Primary Care and General Practice, University of Birmingham, Edgbaston, Birmingham B15 2TT,
b Birmingham Health Authority, Edgbaston, Birmingham B16 9RG, UK and
a Department of General Practice, University College Cork, Ireland.
Jones MI, Greenfield SM, Jowett S, Bradley CP and Seal R. Proton pump inhibitors: a study of GPs' prescribing. Family Practice 2001; 18: 333–338.
Received 19 April 2000; Revised 13 September 2000; Accepted 8 January 2001.
Abstract
Background. There has been a rapid increase in proton pump inhibitor (PPI) prescribing in recent years, and controlling the cost and improving the quality of prescribing is an issue of concern to many GPs.
Objective. Our aim was to compare GPs' usage of different PPIs and explore how GPs' PPI prescribing changes following the introduction of a cheaper competitor.
Methods. PPI prescribing data (PACT) for 53 GPs, who were selected as regular users of a teaching hospital, were monitored from January 1995 to December 1997. The GPs were located in two adjoining health districts and had been interviewed about influences on their decisions to begin prescribing lansoprazole. The PPI prescribing data were collected for the teaching hospital and the general hospital in the adjoining district.
Results. Complete prescribing data were available for 50 GPs. Total PPI prescribing increased throughout the study due mainly to increasing use of the new PPIs. Use of the new PPIs increased from 6 to 24% over 3 years. The proportion of maintenance doses prescribed increased from 3 to 12%. There was a 23-fold difference in total PPI prescribing and an 87-fold difference in lansoprazole prescribing between the highest and lowest prescribers. The uptake of pantoprazole was slower than that of lansoprazole. A rapid increase in the use of lansoprazole by the GPs followed an increase in use in the teaching hospital.
Conclusion. Hospital prescribing was an important influence on the choice of PPI used by GPs. The wide variation in PPI prescribing suggests that there is scope for improvement in the quality and cost of PPI prescribing.
Keywords. General practice, hospital prescribing, prescribing influences, proton pump inhibitors.
Introduction
The use of ulcer-healing drugs has increased greatly in recent years and now accounts for nearly 10% of the annual prescribing costs of £4.5 billion in England.1 From 1993 to 1997, the use of H2 receptor antagonists declined whereas the use of proton pump inhibitors (PPIs) increased 4-fold.1 In 1997, PPIs accounted for 6% of total primary care drug expenditure,2 and there is increasing pressure on GPs to reduce their prescribing costs. The wide variation between GPs in the treatment of dyspepsia and in the use of PPIs 3–6 suggests that there is scope for improving the quality of PPI prescribing for dyspepsia.
As part of a study of factors which influence the introduction of new drugs into clinical practice in primary and secondary care, GPs and consultants were interviewed about their views on prescribing new drugs in general and a range of eight specific new drugs, including lansoprazole.7,8 This paper uses the PPI prescribing data of the GPs who took part to compare their usage of three PPIs (omeprazole, lansoprazole and pantoprazole) and to explore changes in prescribing following the introduction of a cheaper competitor.
Methods
Prescribing data
GPs who were regular users of a large Birmingham teaching hospital (defined as those who had five or more patients discharged during May 1995) were identified from the discharge notes. All 99 GPs identified were approached and 56 (57%), located in Birmingham and an adjoining health district, agreed to participate. PACT (Prescribing Analysis and CosT) catalogue data were obtained, with the GPs' consent, from the Prescription Pricing Authority (PPA) for BNF section 1.3.5 (proton pump inhibitors) for each GP from January 1995 to December 1997. The prescribing data for each drug were converted to defined daily doses (DDDs) to compare the usage of the different drugs.9
The GP cost data for lansoprazole and total PPI prescribing were compared with data for Birmingham Health Authority, the West Midlands Region and England from January 1995 to September 1997, after adjusting for the number of GPs in each of these groups (560, 2815 and 28 481, respectively).10
Prescribing data for lansoprazole were obtained from the pharmacies in the teaching hospital and the general hospital in the adjoining health district (DGH) where 38 consultant (including three gastroenterologists) interviews had taken place.7
Statistical analysis
The data were coded and analysed using SPSS v8. Spearman's rank correlation coefficients (rs) were calculated to assess the association between variables. Forward stepwise multiple regression was used to construct a model to attempt to explain the variation in the amount of total PPIs prescribed, using a significance level of 5% for variable addition using the variables in Table 1
.
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Results
The characteristics of the 50 (89%) GPs for whom complete prescribing data were available are shown in Table 1
. The GPs served areas of greater deprivation than both health districts as a whole.11 Their practices were located mainly in areas with a higher minority ethnic population (range 8–69%), particularly from the Indian subcontinent, than the UK (5.5%) and Birmingham (21.4%) averages.12
The total cost of PPI prescribing by the study GPs was higher than in the West Midlands region and England (Figure 1), but the cost of lansoprazole prescribing was similar (Figure 2). There was a wide variation in the amount of PPIs used by the GPs (Figure 3), with a 23-fold difference between the highest and lowest users (Table 2). Of the independent variables in the multiple regression model, only fundholding status and membership/fellowship of the RCGP were significant and explained only 23% of the variation in total PPIs prescribed. Fundholders were likely to prescribe fewer PPIs, and RCGP members to prescribe slightly more (Table 3).
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The quantity of each drug prescribed per prescription item also showed a wide variation (Table 4
), although 28 and 56 capsules were by far the most common; 84 and 112 capsules (multiples of 28) were also prescribed frequently.
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Total PPI prescribing in DDDs increased steadily over the 3 years (Figure 4
). The most commonly prescribed dosage was omeprazole 20 mg. The use of lansoprazole and the two new PPIs together increased from 6 to 20 and 24% of total PPI prescribing, respectively, during the study. Nationally the use of lansoprazole increased from 5 to 22% over this period. The use of lansoprazole was higher in the teaching hospital (which had undertaken clinical trials of lansoprazole) than the DGH, and higher for Birmingham GPs than for those in the adjoining health district (Figure 5).
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The uptake of lansoprazole was greater than that of pantoprazole; in the 5th quarter after their launch, 39 (78%) GPs had used pantoprazole compared with 44 (88%) GPs who had used lansoprazole. Similarly, the amount of pantoprazole prescribed (4880 DDDs) was lower than for lansoprazole at the same point (5543 DDDs). Thirty-five per cent of the total prescribing of pantoprazole (6722 out of 19 140 DDDs) was due to two GPs in one practice who were involved in a post-marketing study of the drug. Excluding these two GPs, the amount of pantoprazole prescribed in the 5th quarter (3654 DDDs) was only 66% of that of lansoprazole in the corresponding period.
Although the use of both treatment and maintenance doses of PPIs increased steadily throughout the study, the proportion of maintenance doses increased from 3 to 12% of total prescribing, mainly due to increasing use of lansoprazole 15 mg (Figure 6). The proportion of maintenance doses used by each GP ranged from 1.2 to 33.0% of their total PPI prescribing.
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Although there was a trend towards increasing use of the maintenance doses of PPIs with higher overall use of PPIs, the higher total prescribers used a lower proportion of maintenance doses (rs = –0.384, P = 0.005). Similarly, many of the highest prescribers of PPIs used a lower proportion of the newer drugs, but there was no significant association (rs = –0.040, P = 0.783).
Discussion
This study has shown a wide variation between GPs in total PPI prescribing, proportion of newer drugs and maintenance doses used, and, as reported for other drugs,13 range of prescribing per item. Overall, PPI prescribing was higher than regional and national levels. This may be due to the higher than average levels of deprivation and ethnic minorities in their practice populations, factors associated with a higher prevalence of peptic ulcers and oesophageal disease.14
PACT data do not link prescribing to patients and diagnoses, and it was not possible to identify whether a PPI was hospital initiated and whether the choice of PPI was that of a consultant or the GP. Prescribing patterns can be distorted by the effect of a small number of GPs, as shown by the pantoprazole data. Other GP factors which might be expected to influence prescribing are special interests and number of sessions worked. The selection criteria for this study meant that part-time GPs were unlikely to be included in the initial selection. However, two GPs reported that they had a partner with a special interest in gastrointestinal medicine and both had lower than average levels of total PPI prescribing (13 984 and 10 477 DDDs).
Like other studies,15 the results show that GP and practice variables only explain a small proportion of the variation in prescribing costs; however, they suggest that prescribing decisions are complex and idiosyncratic and will not be fully explained by easily identifiable GP characteristics.
The teaching hospital increased its use of lansoprazole throughout the study, as did GPs in the Birmingham health district. In the DGH, lanosprazole was rarely prescribed, and use by GPs in the district was correspondingly less. The rapid rise in GP prescribing of lansoprazole began in March–June 1997, after the increase in use by the teaching hospital, but before a price reduction in June would have shown an effect. This suggests that the choice of PPI by GPs is partly hospital led.
Advice readily available to GPs at the time of the study suggested that there was no significant clinical difference between the PPIs,16–19 and in the interviews GPs reported that cost was an important influence on their decision to use a newer PPI.7 Selective price reductions of the competing brands both during and after this study demonstrate the importance of cost.
The wide variation in the total amount of PPIs prescribed and the amount prescribed per item suggests that some guidance for GPs as to the consensus view of what constitutes ‘good practice’ in PPI prescribing may be helpful, for example the amount of PPI prescribing per ASTRO-PU or the proportion of ulcer-healing drugs from PPIs.20 As the highest overall users of PPIs in this study used a lower proportion of the low-dose formulations and a lower proportion of newer (and cheaper) drugs, there is considerable scope for further prescribing savings among these GPs. The PPI therapeutic group has several important features—perceived efficacy for symptom relief with few side effects, rapidly escalating costs, cost pressure on GPs to reduce prescribing, little difference in efficacy and side effects, and price competition between drugs. Thus conclusions about the introduction of a new competitor in the PPI group may not necessarily be generalizable to other therapeutic groups.
Acknowledgments
We would like to thank the GPs who took part in the study, and Professor Stephen Chapman, Martin Jenkins, the Prescription Pricing Authority and the hospital pharmacists for providing prescribing data. This study was funded by the Department of Health Primary/ Secondary Care Interface Programme.
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