New drugs in general practice: prescribing patterns and external influences

Abstract

In this thesis several studies are presented with the objective to detect and elucidate the patterns by which new drugs are prescribed by general practitioners (GPs). Furthermore, we studied the influences of medical specialists and community pharmacists as important factors on the GP's decision to prescribe new drugs during the first six moths after the drug's market introduction. The reason for why it is important to study the dynamics of prescribing new drugs is that even after years of extensive clinical testing in very specific patients there is still a high degree of uncertainty about the new drug's surplus value in medical practice when the new drug is introduced on the market. This uncertainty not only applies to the new drug's clinical effectiveness, but also to its safety profile when used by 'normal' patients and its socio-economic impact on society in general. The individual and fairly rational decisions of GPs to prescribe new drugs to specific patients may have unintentional consequences in the general patient population. GPs may decide that a new drug is the best option for his/her unique patient that failed to respond satisfactory to older drugs. However, if the majority of the GPs makes similar decisions this can result in the new drug being prescribed to patients for whom the drugs was not developed in the first place. The studies in this thesis resulted in three important findings. First, a small group of GPs seems, despite all reasons to be cautious, responsible for a substantial proportion of all early new drugs prescriptions within the first six months after the drug's market introduction. However, the GP's decisions to prescribe a new drug seem to be very drug dependent. Prescribing one new drug does not seem to be a strong predictor for the GP to prescribe other new drugs as well. This finding contradicts with the concept of the early adopters as being related to a general innovative predisposition. Second, our findings contradict the general and expected concept that the diffusion of new drugs generally follows a two-step model, with hospital specialists as the innovators and GPs as the followers. Although the influence of hospital specialists is clearly visible for new drugs, and often greater than for existing older drugs, the rapid uptake of new drugs may not always be specialist induced. GPs themselves are responsible for a considerable amount of all early prescriptions for new drugs. Third, GPs that participate in pharmacotherapeutic audit meetings with the community pharmacists working in the same neighbourhood prescribe less new drugs. The professional collaboration between GPs and pharmacists seem to be an effective way to control early new drug prescribing in general practice. However, it is vital that GPs and pharmacists set common goals on how to optimise pharmacotherapy. This concordance should be reflected in PTAMs that result in concrete decisions with auditing of GP prescribing behaviour. Pharmacists should take up an active role in organising PTAMs to extent their influence on drug prescribing.