Abstract
An important element of the process by which new drugs achieve widespread use is their adoption by GPs. In this paper, we explore the factors that shape the timing of the first prescription of six new drugs by General Practitioners in Ireland. Our analysis is based on a dataset that matches prescription data with data on GP characteristics. We then use duration analysis to explore both equilibrium and non-equilibrium determinants of prescribing innovation. Our study highlights a range of commonalities across all of the drugs considered and suggests the importance of GP and practice characteristics in shaping prescribing decisions. We also find strongly significant, and consistently signed, stock and order effects across these drugs: GPs who have a track record of early adoption tend also to be early adopters of other new drugs; and, the larger the proportion of GPs which have already adopted a new drug the slower is subsequent adoption. Epidemic and learning effects are also evident with slower adoption by rural practices and among those GPs with narrower prescribing portfolios.
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Notes
Ireland has a low number of GPs per capita in comparison with other EU countries. It is estimated Ireland has approximately 52–56 GPs per 100,000 of the population. Countries such as Austria, France and Germany have over 100 GPs per 100,000. Irish GPs are, however, considered well paid in relation to their EU colleagues; Irish GPs are paid four times the GDP per capita value, a higher multiple than in the UK, Germany, the Netherlands, France and Sweden [5].
In Budget 2010, a new charge of 50% item was announced to be introduced in October 2010. This charge did not apply within the timeframe of this study.
GPs are remunerated for treating GMS patients on a capitation basis. The capitation fees are calculated based on the following factors: (1) a demographic factor designed to reflect differences in demands by various age and gender groups, and (2) a geographic factor designed to reflect the expenses incurred in visiting patients in various age/distance categories [5].
In 2008, the average income for a GP in Ireland with a GMS contract was €220,000 [8].
General practices are not obliged to display the price of a consultation, although an updated Guide to Professional Conduct and Ethics for Registered Medical Practitioners specifies that GPs can display prices. In 2009, the Competition Authority estimated that the average cost of a GP visit for a private patient is approximately €50–55 in urban areas, with slightly lower charges in rural areas [8]. The National Consumer Agency also reported a wide range of prices for GP visits, averaging at €51, with a minimum of €35 and a maximum of €70 [5].
Drugs authorised by the IMB do not automatically receive a GMS code, although most drugs do. This is discussed in more detail in Sect. 3.
We are concerned with the ‘prescribing innovation’, i.e. a GPs decision to prescribe a new drug for the first time rather than the ‘new drug’ innovation.
Irish general practices vary widely in size and personal characteristics with O’Dowd et al. [31] estimating that 35% of general practices were solo-practitioner practices, with the remainder comprising of two GP practices (30%), three GP practices (20%) or four or more GP practices (15%). Not all general practices have nursing and clerical support. 35% of practices employ a full-time nurse and 70% of practices employ full-time clerical assistance. Less than one in three practices employ a practice manager [31].
When a GMS patient gets a prescription from a GP, they fill it either in a pharmacy or, if their GP has a dispensing licence, at the GP practice. The medicine is dispensed free of charge to the patient and a duplicate of the prescription is sent by the dispenser to the GMS (Payments) Board for payment.
Nicotine drugs, nasal sprays and chewing gum, are also available to purchase without prescription.
This may reflect a ‘new year resolution’ effect as people seek support for giving up smoking.
Specifically, the order variables take a value of one where a GP first prescribed one of the other five drugs considered here in the first 6 months after its first adoption. Between 25 and 35% of GPs may be considered ‘first adopters’ and take a value of one in relation to these order variables.
Participation in the Indicative Drug Treatment Scheme was voluntary and GPs retained the right and obligation to prescribe as they considered necessary. No sanctions were in place for those GPs who failed to reduce costs.
In practice, and despite some experimentation, we found that our duration models did not converge when we attempted to control for unobserved heterogeneity. This issue has been noted in the literature [44] and we discuss the implications of this in the following section.
The data analysis and statistical software package Stata 11 is used to conduct the econometric analysis [45].
Given that not all GPs have adopted each drug by the end of the sample period, the data are right-censored. As a robustness check, we removed the non-adopters for each drug from the sample and ran the duration models individually. The same results as those reported were obtained. We are grateful to a referee for highlighting this point.
However, not all small business adoption studies report significant findings in relation to age, For example, Burton et al. [38] report no statistically significant relationship between age of a farmer and the adoption of organic horticultural technology.
Being an early prescriber of one drug in our data does predict early adoption of some drugs. However, it is not a strong predictor of being an early adopter of all drugs examined. For instance, no GP in the sample adopted all six drugs within the first 6 months of them being adopted. This contradicts the image of early adopters as being related to a general innovative predisposition. Therefore, it appears that a GPs decision to prescribe is heavily dependent on the new drugs in question [27, 34].
The Stata command ‘streg’ is used in our analysis. We included the ‘frailty’ option to control for unobserved heterogeneity.
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Acknowledgments
Valuable comments on earlier drafts were received from participants at the Irish Economic Association (IEA) Conference April 2010, the Health Economists Association of Ireland (HEAI) May 2010, the Health Economics Study Group (HESG) June 2010 and a number of New Staff Development Workshops, Department of Economics, University College Cork. Valuable comments were also received from two anonymous referees. We would like to thank Dr. Brendan McElroy for his generous assistance in relation to acquiring the prescribing and GP characteristics databases from the HSE’s Primary Care Reimbursement Service. Opinions and errors in the paper are the sole responsibility of the authors.
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Bourke, J., Roper, S. In with the new: the determinants of prescribing innovation by general practitioners in Ireland. Eur J Health Econ 13, 393–407 (2012). https://doi.org/10.1007/s10198-011-0311-5
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DOI: https://doi.org/10.1007/s10198-011-0311-5
Keywords
- Prescribing innovation
- Equilibrium and non-equilibrium models of adoption
- General practitioners
- Ireland