Trajectories of prices in generic drug markets: what can we infer from looking at trajectories rather than average prices?
Tóm tắt
Well-functioning competitive markets are key to controlling generic drug prices. This is important since over 90% of all drugs sold in the US are generics. Recently, there have been examples of large price increases in the generic market. This paper examines price trajectories for generic drugs using a group-based trajectory modelling approach (GBTM). We fit the model using quarterly price information in the IBM MarketScan claims database for the past decade. We identify three dominant price trajectories for this period: rapid increase trajectories, slow decline and rapid decline. Most generic drugs show a slow or a rapid decline in price trajectories. However, around 17% of all generic drugs show rapid price increase trajectories. As Congress is exploring an excise tax on drugs whose list price increases faster than the rate of inflation, we discuss what drugs would be most likely to be affected by this law.
Tài liệu tham khảo
Allen NB, Siddique J, Wilkins JT, Shay C, Lewis CE, Goff DC, et al. Blood pressure trajectories in early adulthood and subclinical atherosclerosis in middle age. Jama. 2014;311(5):490–7.
Berndt, E. R., Conti, R. M. & Murphy, S. J. (2017), The landscape of us generic prescription drug markets, 2004–2016, Technical report, National Bureau of Economic Research.
Blewett LA, Call KT, Turner J, Hest R. Data resources for conducting health services and policy research. Annu Rev Public Health. 2018;39:437–52.
Cole AL, Sanoff HK, Dusetzina SB. Possible insufficiency of generic price competition to contain prices for orally administered anticancer therapies. JAMA Intern Med. 2017;177(11):1679–80.
Dave CV, Kesselheim AS, Fox ER, Qiu P, Hartzema A. High generic drug prices and market competition: a retrospective cohort study. Ann Intern Med. 2017;167(3):145–51.
DiMasi JA. Price trends for prescription pharmaceuticals: 1995–1999. In: Department of Health and Human Services Conference on pharmaceutical pricing practices, utilization, and costs; 2000.
Federman AD, Halm EA, Zhu C, Hochman T, Siu AL. Association of income and prescription drug coverage with generic medication use among older adults with hypertension. Am J Manag Care. 2006;12(10):611.
Frank, R. G., Hicks, A. & Berndt, E. R. (2019), The price to consumers of generic pharmaceuticals: beyond the headlines, Technical report, National Bureau of Economic Research.
Franklin JM, Shrank WH, Pakes J, Sanfélix-Gimeno G, Matlin OS, Brennan TA, et al. Group-based trajectory models: a new approach to classifying and predicting long-term medication adherence. Med Care. 2013;51(9):789–96.
Hernandez I, Good CB, Cutler DM, Gellad WF, Parekh N, Shrank WH. The contribution of new product entry versus existing product inflation in the rising costs of drugs. Health Aff. 2019;38(1):76–83.
Hu X, Gu S, Sun X, Gu Y, Zhen X, Li Y, et al. Cognitive ageing trajectories and mortality of chinese oldest-old. Arch Gerontol Geriatr. 2019;82:81–7.
Jones BL, Nagin DS. A note on a stata plugin for estimating group-based trajectory models. Sociol Methods Res. 2013;42(4):608–13.
Joyce G, Henkhaus LE, Gascue L, Zissimopoulos J. Generic drug price hikes and out-of-pocket spending for medicare beneficiaries. Health Aff. 2018;37(10):1578–86.
Karas L, Shermock KM, Proctor C, Socal M, Anderson GF. Limited distribution networks stifle competition in the generic and biosimilar drug industries. Am J Manag Care. 2018;24(4):e122–7.
Lakdawalla DN. Economics of the pharmaceutical industry. J Econ Lit. 2018;56(2):397–449.
Mahoney JJ. Reducing patient drug acquisition costs can lower diabetes health claims. Am J Manag Care. 2005;11(5 Suppl):S170–6.
Mandel, M. (2019), The prescription escalator: the real reason why americans pay more for drugs each year, why they are so upset and what can be done about it, Technical report, Progressive Policy Institute.
Nagin DS. Group-based trajectory modeling and criminal career research. J Res Crime Delinquency. 2016;53(3):356–71.
Nagin DS, Nagin D, et al. Group-based modeling of development. Harvard University Press; 2005.
Nagin DS, Odgers CL. Group-based trajectory modeling in clinical research. Annu Rev Clin Psychol. 2010;6:109–38.
Nagin DS, Tremblay RE. What has been learned from group-based trajectory modeling? Examples from physical aggression and other problem behaviors. Ann Am Acad Pol Soc Sci. 2005;602(1):82–117.
Part D. Generic drug prices declined overall, but some had extraordinary price increases. Washington DC: GAO; 2016. p. 16–706.
Porter RH. Detecting collusion. Rev Industrial Organization. 2005;26(2):147–67.
Reiffen D, Ward MR. Generic drug industry dynamics. Rev Econ Stat. 2005;87(1):37–49.
Schondelmeyer SW, Purvis L. Trends in retail prices of brand name prescription drugs widely used by older americans, 2006 to 2015. In: Rx Price watch report; 2016. p. 2016–2.
Selden TM, Abdus S, Miller GE. Decomposing changes in the growth of us prescription drug use and expenditures, 1999-2016. Health Serv Res. 2019;54(4):752-63. https://doi.org/10.1111/1475-6773.13164. Epub 2019 May 9.
Shakil S, Redberg RF. New (very high) prices on old drugs. JAMA Intern Med. 2017;177(11):1568.
Warren JR, Luo L, Halpern-Manners A, Raymo JM, Palloni A. Do different methods for modeling age-graded trajectories yield consistent and valid results? Am J Sociol. 2015;120(6):1809–56.
Zimmer Z, Martin LG, Nagin DS, Jones BL. Modeling disability trajectories and mortality of the oldest-old in China. Demography. 2012;49(1):291–314.