How Quickly Do Physicians Adopt New Drugs? The Case of Second-Generation Antipsychotics

In this study of a large, national sample of prescribers of antipsychotics, we found that a vast majority of prescribers (two-thirds of whom were general practitioners) did not adopt new drugs immediately after they became available. We also found substantial heterogeneity in adoption speed across physicians. In particular, physician specialty and prescribing volume were key drivers of time to adoption, although other factors, such as physicians’ practice setting, training, and demographic characteristics, were also important influences.

Although most second-generation antipsychotics were eventually adopted by a majority of antipsychotic prescribers, a majority of prescribers waited two or more years before prescribing a new product. This behavior could be due to a variety of factors, such as a lack of awareness of a drug’s introduction, a change in prescribing after the U.S. Food and Drug Administration approved new clinical indications, or an intentionally cautious approach to adopting new drugs in an effort to ensure patient safety. Rates of adoption varied by product, however. Variation in adoption rates can be influenced by order of entry and the number of alternatives available in the class. In fact, olanzapine, the third second-generation antipsychotic on the market, was adopted relatively quickly, although we can’t compare its adoption to that of its predecessors, which were introduced before the study period. Variation in adoption by drug can also be influenced by perceived clinical advantages; for example, the relatively rapid adoption of aripiprazole may have been influenced by its relatively low incidence of metabolic side effects (11,26). Rates of reformulation adoption were generally much lower than rates of original formulation adoption, although the physicians who adopted these products did so relatively quickly.

Psychiatrists adopted new antipsychotics much sooner on average and generally prescribed a much broader set of antipsychotics than physicians from other specialties that commonly prescribe antipsychotics. These other specialists may be more likely to prescribe antipsychotics for off-label indications, such as sleep disorders. These results were consistent with those of a study by Taub and colleagues (27), who used a similar data set. The results were also consistent with evidence that physicians often follow norms to guide treatment decisions, for example, prescribing one or two drugs to all patients with a condition, to avoid the substantial costs in time and cognition associated with customized treatment (21,28). Nonpsychiatrists may use norms more commonly than psychiatrists because antipsychotic treatment may represent a much smaller proportion of their prescribing and thus impose greater costs in cognition and time spent learning the nuances of treatment.

Even after controlling for specialty, we found that the highest-volume prescribers were much faster to adopt new products than low-volume prescribers. It could be that high-volume prescribers are disproportionately likely to treat patients with treatment-refractory symptoms and thus more likely to try new products soon after they come on the market. Alternatively, high-volume prescribers may be more likely to be targeted by marketing efforts by drug manufacturers (29,30).

Speed of adoption also varied on the basis of the physician’s practice setting and training. Physicians in solo practice were often slower to adopt new products than those practicing in group settings, although the differences were relatively small. We were unable to isolate the features of solo practice that may contribute to slower adoption. However, physicians who practice alone may have less exposure to a variety of influences on prescribing, including quality improvement initiatives, guideline dissemination, and contact with pharmaceutical sales representatives, than physicians who practice in groups. In addition, social influences within organizations have long been acknowledged as an important determinant of technology diffusion (18,31,32); physicians are likely to be influenced by their peers within their practice organizations, and solo practitioners may have fewer interactions with peers that could influence prescribing behavior.

Interestingly, physicians who graduated from the highest-ranked medical schools were slower to adopt most new antipsychotics. It could be that higher-ranked medical schools are more likely to emphasize a more “conservative” approach to adopting new drugs (33) or grant less exposure to pharmaceutical representatives, but there is no evidence to support this conjecture.

Our study had several limitations. First, we lacked information on the patients’ filling the prescriptions, including the specific disorder for which an antipsychotic was prescribed or the disorder’s severity. Psychiatrists treating patients with treatment-resistant mood or psychotic disorders may be faster adopters than those treating less severely ill patients. Second, we were unable to study the adoption of clozapine and risperidone, although our data allowed us to look at adoption patterns during a 13-year period in which the other second-generation original formulations and most reformulations became available on the market. Third, we lacked data on prescriptions filled by in-hospital pharmacies. Further, to the extent that we did not have data on prescriptions written but not dispensed, our results were confounded by factors affecting patients’ decisions to fill prescriptions. Fourth, we lacked data on the number of free samples distributed by each physician and on use of patient assistance programs, although use of such programs is quite low (34).

In addition, we were unable to identify a physician’s residency training program, which may have more influence on prescribing than medical school attended. Finally, because of a lack of data, we were unable to adjust for some of the external influences on prescribing behavior, such as manufacturer promotional efforts directed at physicians, characteristics of the specific organizations in which physicians practice, and health plan coverage of different antipsychotics.

Physician decisions about whether to adopt new drugs into practice can have profound implications for patient care, in terms of both the quality and the safety of care. These decisions also have important implications for health care spending. As policy makers and payers grapple with how to control rising health care expenditures, there will likely be increased pressure to maximize the value of care received by patients, including individuals with mental disorders. By identifying physician characteristics associated with decisions to adopt new medications, our findings enable the targeting of efforts to increase high-value, evidence-based prescribing through training and education programs, academic detailing (35), guideline dissemination, financial incentives, utilization management, or other initiatives.

This work was supported by a grant from the National Institute of Mental Health (R01 MH093359), by a Robert Wood Johnson Foundation Investigator Award in Health Policy Research to Dr. Huskamp, and by grants to Dr. Donohue from the Agency for Healthcare Research and Quality (R01HS017695) and the National Institute of Mental Health (NIMH) (R34 MH082682 and P30 MH090333), to Dr. Horvitz-Lennon from NIMH (R01 MH087488), and to Dr. Berndt from the National Science Foundation (0915674). The study is based in part on data obtained under license from IMS Health, Inc. (Xponent, 1996–2008). The statements, findings, conclusions, views, and opinions contained and expressed herein are not necessarily those of IMS Health Inc. or any of its affiliated or subsidiary entities.

Dr. Donohue consulted for the National Railways Labor Conference, which was considering changes to its health benefits for railway workers, in 2011. The other authors report no competing interests.