Session: Determinants of Physician Prescribing Decisions
Room: Upson 215
Time: Mon 08:30-10:00

Presenter: Haiden Huskamp (Harvard University. )

Discussant: Marisa Domino (University of North Carolina, Chapel Hill)

Abstract

Psychiatric medications are known to have highly heterogeneous treatment response. Large-scale effectiveness trials indicate that several medication trials are often required before an adequate agent and dose are identified for a particular patient. Studies suggest that, in general, physician preferences for medications used for a particular indication can be quite stable and resistant to change, which has implications for physicians’ willingness to try new agents for their patients who are not responsive to initial treatment choice. However, little is known about whether physicians who prescribe psychiatric medications use the full range of available options for a given indication and whether this varies across specialty. Little is also known about how physician characteristics are associated with the pattern of adoption of new psychiatric medications by physicians. The study’s objectives are to examine the concentration of physician prescribing within a class of psychiatric medications and factors influencing the speed of adoption of new psychiatric medications by physicians.

We use monthly physician-level data from IMS Health on the number of filled prescriptions for a national random sample of 22,257 physicians from one of the ten specialties with the highest antipsychotic prescribing rates over the period 1996-2008. We link these data with information on physician characteristics from the AMA Masterfile, focusing on physicians who prescribed at least one antipsychotic. We first examine concentration of prescribing overall and by physician characteristics, including specialty. We then estimate generalized linear models of the share of a physician’s antipsychotic prescriptions accounted for by each new medication after its introduction, controlling for physician characteristics (age, sex, practice setting, specialty), region, share of antipsychotic promotional expenditures, and events such as release of new information on relative efficacy of antipsychotics.

We found that the four most commonly-prescribed medications (Seroquel, Risperdal, Abilify, and Zyprexa) comprised approximately two-thirds of the market in 2008. The market was even more concentrated at the physician-level. The top four drugs made up 77% of prescriptions written by general practitioners, 78% of those written by psychiatrists, 92% written by pediatricians and 80% by other physicians. Only 4 of 20 antipsychotics were prescribed at least once by a majority of physicians in the sample. The concentration of prescribing differed across specialties. For example, the median number of different antipsychotics prescribed in a month varies by specialty, at 9 for psychiatrists, 5 for general practitioners, 4 for neurologists, and 2 for pediatricians. The market share of the top two drugs was 55% for general practitioners, 50% for psychiatrists, 74% for pediatricians, and 64% for neurologists.

In conclusion, we found that the antipsychotic market is heavily concentrated, with only a handful of drugs accounting for the majority of prescriptions. There were important differences in prescribing patterns across specialties. Psychiatrists typically used a much broader set of medications, while many pediatricians and neurologists prescribed only a couple of different medications. Our findings have important implications for quality improvement initiatives and efforts to improve compliance with treatment guidelines and point to potential difficulties in altering physician preferences for medications.

Presenter bio: Haiden A. Huskamp, Ph.D. is associate professor of health care policy in the Department of Health Care Policy at Harvard Medical School. Her research is focused in three primary areas: 1) mental health policy; 2) prescription drug policy; and 3) the financing and utilization of end-of-life care services. Dr. Huskamp has developed a body of research on the impact of pharmacy management tools used to control drug costs on drug utilization, cost, and quality of care. She currently serves as Principal Investigator for an R01 funded by the National Institute on Aging to examine the impact of Medicare Part D plan generosity on health outcomes among nursing home residents. She recently completed a Career Development Award from the National Institute of Mental Health focused on the economics of psychotropic medications. Through a Robert Wood Johnson Foundation Investigator Award in Health Policy Research, Dr. Huskamp is currently comparing the social costs and benefits of newer psychotropic drugs to assess their social value and identify ways that the value of psychotropic drug spending can be increased. She currently serves as a member of the Institute of Medicine Committee on Accelerating Rare Diseases Research and Orphan Products Development.

Key Terms

physician prescribing; antipsychotics; technology adoption

Authors:

Haiden Huskamp (Harvard University)