In with the new: the determinants of prescribing innovation by general practitioners in Ireland.

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.