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Figure.
Geographic Distribution of Opioid Prescriptions Written per Physician
Geographic Distribution of Opioid Prescriptions Written per Physician

Geographic distribution of opioid prescribing patterns from 2013 to 2015 across the United States based on the mean number of opioid prescriptions written per physician. These data include all physicians whose individual-level data were available.

Table 1.  
Number of Opioid Prescriptions Written by Ophthalmologists From 2013 to 2015
Number of Opioid Prescriptions Written by Ophthalmologists From 2013 to 20154
Table 2.  
Opioid Prescribing Patterns Categorized by Number of Prescriptions Written
Opioid Prescribing Patterns Categorized by Number of Prescriptions Written4
Table 3.  
Variation in Opioid Prescribing Patterns by State From 2013 to 2015
Variation in Opioid Prescribing Patterns by State From 2013 to 20154
1.
 Prescription opioid overdose data. Centers for Disease Control and Prevention. https://www.cdc.gov/drugoverdose/data/overdose.html. Accessed August 24, 2017.
2.
Rudd  RA, Seth  P, David  F, Scholl  L.  Increases in drug and opioid-involved overdose deaths: United States, 2010-2015.  MMWR Morb Mortal Wkly Rep. 2016;65(5051):1445-1452.PubMedGoogle ScholarCrossref
3.
Cicero  TJ, Ellis  MS, Surratt  HL, Kurtz  SP.  The changing face of heroin use in the United States: a retrospective analysis of the past 50 years.  JAMA Psychiatry. 2014;71(7):821-826.PubMedGoogle ScholarCrossref
4.
 Medicare provider utilization and payment data: part D prescriber. Centers for Medicare and Medicaid Services. https://www.cms.gov/Research-Statistics-Data-and-Systems/Statistics-Trends-and-Reports/Medicare-Provider-Charge-Data/Part-D-Prescriber.html. Accessed August 25, 2017.
5.
Manchikanti  L, Helm  S  II, Fellows  B,  et al.  Opioid epidemic in the United States.  Pain Physician. 2012;15(3)(suppl):ES9-ES38.PubMedGoogle Scholar
6.
Volkow  ND, McLellan  TA, Cotto  JH, Karithanom  M, Weiss  SR.  Characteristics of opioid prescriptions in 2009.  JAMA. 2011;305(13):1299-1301.PubMedGoogle ScholarCrossref
7.
Daubresse  M, Chang  HY, Yu  Y,  et al.  Ambulatory diagnosis and treatment of nonmalignant pain in the United States, 2000-2010.  Med Care. 2013;51(10):870-878.PubMedGoogle ScholarCrossref
8.
Levy  B, Paulozzi  L, Mack  KA, Jones  CM.  Trends in opioid analgesic-prescribing rates by specialty, US, 2007-2012.  Am J Prev Med. 2015;49(3):409-413.PubMedGoogle ScholarCrossref
9.
Clarke  H, Soneji  N, Ko  DT, Yun  L, Wijeysundera  DN.  Rates and risk factors for prolonged opioid use after major surgery: population based cohort study.  BMJ. 2014;348:g1251.PubMedGoogle ScholarCrossref
10.
Alam  A, Gomes  T, Zheng  H, Mamdani  MM, Juurlink  DN, Bell  CM.  Long-term analgesic use after low-risk surgery: a retrospective cohort study.  Arch Intern Med. 2012;172(5):425-430.PubMedGoogle ScholarCrossref
11.
Sun  EC, Darnall  BD, Baker  LC, Mackey  S.  Incidence of and risk factors for chronic opioid use among opioid-naive patients in the postoperative period.  JAMA Intern Med. 2016;176(9):1286-1293.PubMedGoogle ScholarCrossref
12.
Porela-Tiihonen  S, Kokki  H, Kaarniranta  K, Kokki  M.  Recovery after cataract surgery.  Acta Ophthalmol. 2016;94(suppl 2):1-34.PubMedGoogle ScholarCrossref
13.
Porela-Tiihonen  S, Kaarniranta  K, Kokki  H.  Postoperative pain after cataract surgery.  J Cataract Refract Surg. 2013;39(5):789-798.PubMedGoogle ScholarCrossref
14.
Mentens  R, Stalmans  P.  Comparison of postoperative comfort in 20 gauge vs 23 gauge pars plana vitrectomy.  Bull Soc Belge Ophtalmol. 2009;(311):5-10.PubMedGoogle Scholar
15.
Wimpissinger  B, Kellner  L, Brannath  W,  et al.  23-Gauge vs 20-gauge system for pars plana vitrectomy: a prospective randomised clinical trial.  Br J Ophthalmol. 2008;92(11):1483-1487.PubMedGoogle ScholarCrossref
16.
Rizzo  S, Genovesi-Ebert  F, Murri  S,  et al.  25-Gauge, sutureless vitrectomy and standard 20-gauge pars plana vitrectomy in idiopathic epiretinal membrane surgery: a comparative pilot study.  Graefes Arch Clin Exp Ophthalmol. 2006;244(4):472-479.PubMedGoogle ScholarCrossref
17.
Porela-Tiihonen  S, Kaarniranta  K, Kokki  M, Purhonen  S, Kokki  H.  A prospective study on postoperative pain after cataract surgery.  Clin Ophthalmol. 2013;7:1429-1435.PubMedGoogle Scholar
18.
Sadiq  SA, Stevenson  L, Gorman  C, Orr  GM.  Use of indomethacin for pain relief following scleral buckling surgery.  Br J Ophthalmol. 1998;82(4):429-431.PubMedGoogle ScholarCrossref
19.
McDonald  DC, Carlson  K, Izrael  D.  Geographic variation in opioid prescribing in the US.  J Pain. 2012;13(10):988-996.PubMedGoogle ScholarCrossref
20.
Shah  A, Hayes  CJ, Martin  BC.  Characteristics of initial prescription episodes and likelihood of long-term opioid use: United States, 2006-2015.  MMWR Morb Mortal Wkly Rep. 2017;66(10):265-269.PubMedGoogle ScholarCrossref
21.
Sastry  SM, Chiang  YP, Javitt  JC.  Practice patterns of the office-based ophthalmologist.  Ophthalmic Surg. 1994;25(2):76-81.PubMedGoogle Scholar
22.
Etzioni  DA, Liu  JH, Maggard  MA, Ko  CY.  The aging population and its impact on the surgery workforce.  Ann Surg. 2003;238(2):170-177.PubMedGoogle Scholar
23.
Campbell  CI, Weisner  C, Leresche  L,  et al.  Age and gender trends in long-term opioid analgesic use for noncancer pain.  Am J Public Health. 2010;100(12):2541-2547.PubMedGoogle ScholarCrossref
24.
Parsells Kelly  J, Cook  SF, Kaufman  DW, Anderson  T, Rosenberg  L, Mitchell  AA.  Prevalence and characteristics of opioid use in the US adult population.  Pain. 2008;138(3):507-513.PubMedGoogle ScholarCrossref
Original Investigation
November 2017

Association Between Opioid Prescribing Patterns and Abuse in Ophthalmology

Author Affiliations
  • 1Vanderbilt Eye Institute, Nashville, Tennessee
JAMA Ophthalmol. 2017;135(11):1216-1220. doi:10.1001/jamaophthalmol.2017.4055
Key Points

Question  What are the trends in opioid prescribing among ophthalmologists?

Findings  In this observational cohort study, we analyzed Medicare Part D Prescription Drug Program beneficiaries from 2013 to 2015 and found that 88% to 89% of ophthalmologists wrote 10 opioid prescriptions or fewer annually. Southern states in the United States tended to have a higher number of prescriptions written per physician.

Meaning  These results suggest ophthalmologists in general prescribe opioids responsibly; the current prescription opioid epidemic should prompt physicians to consider revisiting their opioid prescribing protocols.

Abstract

Importance  Drug overdoses have become the number 1 cause of mortality in American adults 50 years and younger. Prescription opioid abuse is a growing concern that has garnered widespread attention among policymakers and the general public.

Objective  To determine the opioid prescribing patterns among ophthalmologists and elucidate their role in the prescription opioid abuse epidemic.

Design, Setting, and Participants  In this observational cohort study, beneficiaries and their physicians were analyzed using 2013 to 2015 Medicare Part D Prescriber Data. The Centers for Medicare and Medicaid Services Medicare Part D Prescriber Public Use Files for 2013, 2014, and 2015 were accessed. Analysis began in June 2017. Data were collected and analyzed regarding the prescribing patterns for opioid drugs (eg, number of prescriptions written including refills, number of days’ supply, and prescriber rates) for all participating ophthalmologists.

Main Outcomes and Measures  The mean number of opioid prescriptions written annually by ophthalmologists; prescriber rates compared with all prescriptions written; and geographic distribution of opioid prescriptions written per ophthalmologist.

Results  In 2013, 4167 of 19 615 ophthalmologists were women (21.2%). Consistently, most ophthalmologists (88%-89%) wrote 10 opioid prescriptions or fewer annually. Approximately 1% (0.94%-1.03%) of ophthalmologists wrote more than 100 prescriptions per year. On average, ophthalmologists wrote 7 opioid prescriptions per year (134 290 written annually by 19 638 physicians, on average) with a mean supply of 5 days. The 6 states with the highest volume of opioid prescriptions written annually per ophthalmologist were located in the southern United States.

Conclusions and Relevance  In general, ophthalmologists show discretion in their opioid prescribing patterns. The present opioid abuse epidemic should prompt physicians to consider revisiting their prescribing protocols given the high risk for dependency.

Introduction

The present opioid use epidemic has garnered significant attention. Over the last 16 years, more than 183 000 Americans have died from overdose related to prescription opioid use.1,2

The epidemic has set off ripples among policy makers. The US Food and Drug Administration has launched the Opioid Policy Steering Committee to explore and develop strategies to confront the crisis. The committee looks to answer, among other things, whether physicians are informed adequately regarding prescribing recommendations and whether clinicians are prescribing the appropriate number of doses for a given medical indication.

Most people who eventually become addicted to opioids are first exposed through prescription medications.3 Efforts to combat the current situation are now being focused on the pharmaceutical industry supplying the medications and physicians who are doing the prescribing. We set forth to understand better the opioid prescribing habits of ophthalmologists and seek to better elucidate our role in the prescription opioid abuse epidemic.

Methods

The Centers for Medicare and Medicaid Services’ Medicare Provider Utilization and Payment Data were accessed to gather the data for analysis, starting in June 2017. Specifically, we analyzed Medicare Part D Prescriber data4 for 2013 to 2015 (the only years in which data are available). The Part D Prescriber Public Use File provides data on drugs prescribed by physicians and other health care professionals paid for under the Medicare Part D Prescription Drug Program.

The prescriber type was limited to individual ophthalmologists with valid National Provider Identifier numbers practicing in the United States. The data set matched physicians’ National Provider Identifier numbers and the specific prescriptions dispensed at their direction. Data were collected and analyzed regarding the individual prescribing patterns for opioid drugs (number of prescriptions written including refills, number of days’ supply, and prescriber rate). The number of prescriptions for each physician is reported if no prescriptions are written or more than 10 are written for the calendar year. All physicians prescribing 1 to 10 opioid prescriptions during a calendar year are grouped together without providing individual-level prescribing data. This is a measure from the Centers for Medicare and Medicaid Services to protect privacy. To include in the analysis those physicians for which individual-level data were not available (eg, those prescribing between 1 to 10 opioid prescriptions), we estimated 5 prescriptions written annually.

The study was deemed exempt by the institutional review board at Vanderbilt University Medical Center because this was a quality improvement study. Informed consent was not necessary because all data were publicly available and deidentified. The Public Use File was downloaded and organized into Microsoft Excel (Microsoft Corp). Data analysis and figure construction was performed using GraphPad Prism (GraphPad Software). Mean, median, and range calculations were performed for all quantitative variables.

Results
Number of Ophthalmologists

The Medicare Part D prescriber Public Use Files for 2013, 2014, and 2015 included 19 615, 19 587, and 19 712 ophthalmologists, respectively. Age and race/ethnicity data were unavailable. In 2013, 4167 of 19 615 ophthalmologists were women (21.2%).

Number of Opioid Prescriptions

The mean number of opioid prescriptions including refills written by ophthalmologists did not change over the 3-year study period (Table 1). In 2013, 95 898 prescriptions were written by ophthalmologists writing more than 10 opioid prescriptions, compared with 90 534 opioid prescriptions in 2015. The number of ophthalmologists prescribing more than 10 opioid prescriptions was tabulated from the data files. We then used these numbers to calculate the number of prescriptions written per ophthalmologist. For this subset, 41 to 44 opioid prescriptions were written per ophthalmologist per year during the 3-year study period. The mean number of days’ supply that opioid prescriptions were written for was 5. In this subgroup of ophthalmologists, opioid prescriptions represented 8% (mean) of their total prescriptions written annually. The median prescriber rate was 4%, implying the mean was skewed higher by certain prolific opioid prescribers.

No individual prescribing data were given for ophthalmologists writing 1 to 10 opioid prescriptions in a given year. If we assume that these prescribers wrote 5 prescriptions a year on average, the number of opioid prescriptions written per ophthalmologist decreases to 7 per year.

Ophthalmologists’ Prescribing Patterns

Ophthalmologists were separated into 4 categories based on the number of opioid prescriptions written per year: none, 1 to 10, 11 to 100, and more than 100 (Table 2). This was then compared with the total number of prescribing ophthalmologists for the year. During the 3 years, 52 312 of 58 914 ophthalmologists (88.8%) wrote 10 prescriptions or fewer per year. In total, 6023 (10.2%) wrote 11 to 100 opioid prescriptions annually. Each year, approximately 1.0% of ophthalmologists wrote more than 100 opioid prescriptions (Table 2). These numbers stayed consistent between 2013 (191 of 19 615 [0.97%]), 2014 (203 of 19 587 [1.03%]), and 2015 (185 of 19 712 [0.94%]).

Geographic Disparity in Prescribing Patterns

The data available were stratified based on geographic location of the ophthalmologist. The number of opioid prescriptions written overall in the state was averaged against the number of physicians from that state in the database. The analysis was limited to ophthalmologists writing more than 10 opioid prescriptions a year. See the Figure for the geographic distribution across the United States. Oklahoma, Arkansas, Alabama, Tennessee, Georgia, and Texas consistently had the highest number of prescriptions written per physician annually. North Dakota, South Dakota, Iowa, Vermont, Alaska, and Wyoming had the lowest number of opioid prescriptions written per physician between 2013 and 2015 (Table 3).

Discussion

Drug overdoses have become the number 1 cause of mortality in American adults 50 years and younger. Policy makers are now trying to address the root cause of the opioid abuse epidemic. Although a full discussion of the causes of this crisis is beyond the scope of this article, the heavy emphasis on pain control, along with the misuse of prescription opioids, are implicated.5

Primary care physicians, based on sheer volume, prescribe the most opioids.6,7 However, certain specialties, such as dentistry and pain management, specifically have high opioid prescribing rates compared with overall prescriptions written. Opioid prescriptions comprised approximately 8% of prescriptions written by ophthalmologists, on average. However, accounting for outliers, the median number of opioid prescriptions compared with total prescriptions was 4%. This number is below the national mean of 6.8% among all prescribers.8 Additionally, this number is considerably lower compared with other surgical services, in which up to 37% of prescriptions written are for opioids.

Although certain surgical specialties, such as dentistry, may have high prescribing rates, the days supplied is important in mitigating abuse. Among all health care professionals for which data were available, ophthalmologists typically prescribe 5-day supplies of opioids. It is reasonable to assume that these are prescribed for the immediate postoperative period after eye surgery. Although postoperative pain control is an important consideration, there is a known link between surgery and chronic opioid use.9 One such study showed that patients receiving an opioid prescription within 7 days of ambulatory surgery (cataract surgery was 1 of the included procedures) were 44% more likely to become long-term opioid users.10 Although health care professionals are trained to identify patients with signs of opioid dependency, even opioid-naive patients can be at risk for dependence after surgery.11

Pain after cataract surgery is typically minimal, especially with the widespread implementation of small incision phacoemulsification.12,13 The advent of sutureless small-gauge vitrectomy has also led to a significant reduction in postoperative pain.14-16 Nonopioid pain relievers, such as acetaminophen and nonsteroidal anti-inflammatory drugs, frequently control postoperative discomfort.17,18 Although certain ophthalmic procedures may require stronger medications in the immediate postoperative period, this is certainly not the norm. Health care professionals are tasked with individualizing pain control regimens through the judicious use of opioid medications.

Our analysis demonstrates variability in prescribing patterns among ophthalmologists based on region in the United States. Southern states tended to have an increased number of opioid prescriptions written per physician. This is consistent with overall physician opioid prescribing patterns, which are disproportionately higher in southern states.19 Conversely, midwestern states had an overall lower number of opioid prescriptions written per physician. This analysis specifically included physicians writing more than 10 opioid prescriptions annually, as individual data were not available for those prescribing less frequently. These numbers are greatly influenced by certain outliers whose opioid prescriptions comprise 20% or more of all prescriptions written. However, our analysis shows that if all physicians are included, opioid prescribing makes up a minimal amount of overall prescriptions in ophthalmology, with a mean of 7 prescriptions written annually by each physician.

Limitations

The limits of our study relate to the database and information available. The Medicare Part D Prescriber Public Use File is derived from beneficiaries participating in the Medicare Part D prescription drug program. Physicians not participating in Medicare Part D are not included. Although this database encompasses approximately 70% of all Medicare beneficiaries, some patients were missed. Additionally, this analysis does not take into account patients with private insurance or individuals without insurance. Any aggregated data from prescribers with 10 or fewer claims are excluded from the database (a measure from the Centers for Medicare and Medicaid Services to protect patient privacy). We acknowledge that the statistics may be skewed by certain high-volume prescribers. This is especially true given the number of physicians who did not record any opioid prescriptions. Additionally, we cannot account for physicians who may be retired or no longer practicing but still listed in the Medicare Part D database.

However, despite these limitations, ophthalmologists appear to be cautious prescribers of opioids compared with their surgical peers. Consistently between 2013 to 2015, almost 90% of ophthalmologists wrote 10 or fewer opioid prescriptions annually with half of this group recording no such prescriptions. The mean supply of 5 days also shows appropriate discretion. However, even with a limited 5-day supply, up to 10% of patients can become chronic opioid users at 1 year.20 The evidence shows that each incremental increase in initial opioid supply leads to a dramatic increase in the risk of dependency.

Ophthalmology is a specialty in which a disproportionate amount of care is provided to patients over age 65 years.21,22 Although opioid overdose rates are highest among people aged 25 to 54 years, chronic opioid abuse among older age groups is a growing concern.23,24 This further underscores the importance of thoughtful opioid prescribing.

Conclusions

Our findings imply that ophthalmologists, as a group, tend to prescribe opioids responsibly to their patients. Advancements in ophthalmic surgery have kept opioid prescribing rates stagnant across the profession while many other surgical specialties’ rates continue to rise. However, the current epidemic highlights the substantial risk of opioid dependency even with seemingly innocuous prescribing patterns. The current state of affairs should prompt health care professionals to consider revisiting their protocols for opioid prescribing.

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Article Information

Corresponding Author: Shriji Patel, MD, Vanderbilt Eye Institute, 2311 Pierce Ave, Nashville, TN 37232 (shriji.patel@vanderbilt.edu).

Accepted for Publication: August 19, 2017.

Published Online: October 5, 2017. doi:10.1001/jamaophthalmol.2017.4055

Author Contributions: Drs Patel and Sternberg had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Both authors.

Acquisition, analysis, or interpretation of data: Patel.

Drafting of the manuscript: Patel.

Critical revision of the manuscript for important intellectual content: Both authors.

Statistical analysis: Patel.

Administrative, technical, or material support: Both authors.

Conflict of Interest Disclosures: Both authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

References
1.
 Prescription opioid overdose data. Centers for Disease Control and Prevention. https://www.cdc.gov/drugoverdose/data/overdose.html. Accessed August 24, 2017.
2.
Rudd  RA, Seth  P, David  F, Scholl  L.  Increases in drug and opioid-involved overdose deaths: United States, 2010-2015.  MMWR Morb Mortal Wkly Rep. 2016;65(5051):1445-1452.PubMedGoogle ScholarCrossref
3.
Cicero  TJ, Ellis  MS, Surratt  HL, Kurtz  SP.  The changing face of heroin use in the United States: a retrospective analysis of the past 50 years.  JAMA Psychiatry. 2014;71(7):821-826.PubMedGoogle ScholarCrossref
4.
 Medicare provider utilization and payment data: part D prescriber. Centers for Medicare and Medicaid Services. https://www.cms.gov/Research-Statistics-Data-and-Systems/Statistics-Trends-and-Reports/Medicare-Provider-Charge-Data/Part-D-Prescriber.html. Accessed August 25, 2017.
5.
Manchikanti  L, Helm  S  II, Fellows  B,  et al.  Opioid epidemic in the United States.  Pain Physician. 2012;15(3)(suppl):ES9-ES38.PubMedGoogle Scholar
6.
Volkow  ND, McLellan  TA, Cotto  JH, Karithanom  M, Weiss  SR.  Characteristics of opioid prescriptions in 2009.  JAMA. 2011;305(13):1299-1301.PubMedGoogle ScholarCrossref
7.
Daubresse  M, Chang  HY, Yu  Y,  et al.  Ambulatory diagnosis and treatment of nonmalignant pain in the United States, 2000-2010.  Med Care. 2013;51(10):870-878.PubMedGoogle ScholarCrossref
8.
Levy  B, Paulozzi  L, Mack  KA, Jones  CM.  Trends in opioid analgesic-prescribing rates by specialty, US, 2007-2012.  Am J Prev Med. 2015;49(3):409-413.PubMedGoogle ScholarCrossref
9.
Clarke  H, Soneji  N, Ko  DT, Yun  L, Wijeysundera  DN.  Rates and risk factors for prolonged opioid use after major surgery: population based cohort study.  BMJ. 2014;348:g1251.PubMedGoogle ScholarCrossref
10.
Alam  A, Gomes  T, Zheng  H, Mamdani  MM, Juurlink  DN, Bell  CM.  Long-term analgesic use after low-risk surgery: a retrospective cohort study.  Arch Intern Med. 2012;172(5):425-430.PubMedGoogle ScholarCrossref
11.
Sun  EC, Darnall  BD, Baker  LC, Mackey  S.  Incidence of and risk factors for chronic opioid use among opioid-naive patients in the postoperative period.  JAMA Intern Med. 2016;176(9):1286-1293.PubMedGoogle ScholarCrossref
12.
Porela-Tiihonen  S, Kokki  H, Kaarniranta  K, Kokki  M.  Recovery after cataract surgery.  Acta Ophthalmol. 2016;94(suppl 2):1-34.PubMedGoogle ScholarCrossref
13.
Porela-Tiihonen  S, Kaarniranta  K, Kokki  H.  Postoperative pain after cataract surgery.  J Cataract Refract Surg. 2013;39(5):789-798.PubMedGoogle ScholarCrossref
14.
Mentens  R, Stalmans  P.  Comparison of postoperative comfort in 20 gauge vs 23 gauge pars plana vitrectomy.  Bull Soc Belge Ophtalmol. 2009;(311):5-10.PubMedGoogle Scholar
15.
Wimpissinger  B, Kellner  L, Brannath  W,  et al.  23-Gauge vs 20-gauge system for pars plana vitrectomy: a prospective randomised clinical trial.  Br J Ophthalmol. 2008;92(11):1483-1487.PubMedGoogle ScholarCrossref
16.
Rizzo  S, Genovesi-Ebert  F, Murri  S,  et al.  25-Gauge, sutureless vitrectomy and standard 20-gauge pars plana vitrectomy in idiopathic epiretinal membrane surgery: a comparative pilot study.  Graefes Arch Clin Exp Ophthalmol. 2006;244(4):472-479.PubMedGoogle ScholarCrossref
17.
Porela-Tiihonen  S, Kaarniranta  K, Kokki  M, Purhonen  S, Kokki  H.  A prospective study on postoperative pain after cataract surgery.  Clin Ophthalmol. 2013;7:1429-1435.PubMedGoogle Scholar
18.
Sadiq  SA, Stevenson  L, Gorman  C, Orr  GM.  Use of indomethacin for pain relief following scleral buckling surgery.  Br J Ophthalmol. 1998;82(4):429-431.PubMedGoogle ScholarCrossref
19.
McDonald  DC, Carlson  K, Izrael  D.  Geographic variation in opioid prescribing in the US.  J Pain. 2012;13(10):988-996.PubMedGoogle ScholarCrossref
20.
Shah  A, Hayes  CJ, Martin  BC.  Characteristics of initial prescription episodes and likelihood of long-term opioid use: United States, 2006-2015.  MMWR Morb Mortal Wkly Rep. 2017;66(10):265-269.PubMedGoogle ScholarCrossref
21.
Sastry  SM, Chiang  YP, Javitt  JC.  Practice patterns of the office-based ophthalmologist.  Ophthalmic Surg. 1994;25(2):76-81.PubMedGoogle Scholar
22.
Etzioni  DA, Liu  JH, Maggard  MA, Ko  CY.  The aging population and its impact on the surgery workforce.  Ann Surg. 2003;238(2):170-177.PubMedGoogle Scholar
23.
Campbell  CI, Weisner  C, Leresche  L,  et al.  Age and gender trends in long-term opioid analgesic use for noncancer pain.  Am J Public Health. 2010;100(12):2541-2547.PubMedGoogle ScholarCrossref
24.
Parsells Kelly  J, Cook  SF, Kaufman  DW, Anderson  T, Rosenberg  L, Mitchell  AA.  Prevalence and characteristics of opioid use in the US adult population.  Pain. 2008;138(3):507-513.PubMedGoogle ScholarCrossref
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