Characteristics of patients using extreme opioid dosages in the treatment of chronic low back pain

Shannon Essler, Southwestern University, Georgetown
Terrell Benold, M.D., UT Southwestern – Austin FMRP
Sandra Burge, Ph.D., Department of Family and Community Medicine, UTHSCSA

INTRODUCTION

In the United States alone, physicians see two million annual cases of back pain. Low back pain ranks second only to respiratory illness as a reason to visit primary care providers.(1) Recent studies document a 423-percent increase in opioid expenditures for back pain.(2) While constituting only 4.6 percent of the world’s population, Americans have been consuming 80 percent of the global opioid supply and 99 percent of the global hydrocodone supply, despite continued research that indicates the repercussions of chronic opioid treatment.(3) Specific deterrents include constipation, nausea, vomiting, respiratory depression, drug abuse, drug diversion, addiction, and opioid-induced hyperalgesia (OIH).(3,4)

Abuse of prescription opioids among teens has increased an astounding 542 percent between 1992 and 2003. During this same period, there was a 90-percent increase (from 7.8 million to 14.8 million) in the number of Americans who admitted abusing controlled prescription drugs.(5) A large study of over 14,000 patients found evidence to suggest that 20.1 percent to 53.(6) percent of patients treated for chronic non-cancer pain diverted their prescribed narcotics.(6) Other reports have also documented the characteristics of patients most likely to abuse or divert prescribed opioids (e.g. anxiety, depression, history of drug abuse).(7,8,9)

The prescribing of opioids for chronic, non-malignant pain often varies dramatically among physicians.(10) This is likely due to the subjective nature of non-cancer pain complaints, as well as a historical lack of clear, concrete guidelines regarding the appropriateness of opioid prescribing. A few studies have recorded the average opioid dosage used in treating chronic low back pain (CLBP) in primary care populations. However, only one study, published in 2008, has ever provided evidence to suggest an opioid dose beyond which patients might suffer decreased functionality and quality of life. The results of this study suggest an opioid ceiling for most patients of 40 mg per day in morphine equivalence. While functionality of patients taking greater than 40 mg per day suffered, patients taking 105 mg or more per day suffered to an even greater extent.(11)

In this study of patients with CLBP, we assess characteristics that may differentiate patients taking extremely high doses of opioid medication (in the top 10 percent) from those taking lower doses and patients taking none at all. We examine differences in demographic characteristics, treatments for pain, comorbidities, and pain and health outcomes.

METHODS

Subjects. In 2008, student research assistants consented and enrolled 213 outpatients with CLBP from six family medicine residency programs in the Residency Research Network of Texas. Eligible patients had low back pain for three months or longer; investigators excluded pregnant women and patients with cancer. In 2009, student research assistants conducted one-year follow-up data collection from medical records of 204 participants (96 percent follow-up), and surveys of 137 participants (64 percent follow-up).

Procedure. In 2008, students enrolled, consented, and surveyed patients as they arrived for routine outpatient visits. Immediately following the visit, students abstracted study data from participants’ medical records. For the one-year follow-up, the medical records were revisited and data abstracted from the past 12 months. In addition, patients were contacted again and surveyed by telephone or during return clinic visits.

Measurement. From participants’ medical records, students gathered information about causes of low back pain, medical and procedural treatments for pain, comorbidities, and BMI. The dosages of the various opioids used by the CLBP patients were converted to daily morphine equivalence using the tool shown in Table 1.

A five-page patient survey addressed demographic characteristics, pain duration, frequency and severity, physical functioning and general health (from the MOS-SF 36), screening questions for anxiety and depression (PHQ-2), substance abuse, and risk for opioid abuse (SOAPP).(12,13,14)

Analysis. In this analysis, participants were divided into three groups: non-users of opioid medication (N = 100); moderate users (115 mg or less per day in morphine equivalence, N = 93); and high users, the top 10 percent of users (greater than 115 mg per day, N = 11). Differences between the three groups with regard to demographic characteristics, other treatments for pain, and comorbidities were analyzed using chi-square analysis and AVOVA. The 137 surveys completed were examined to assess group differences in pain and physical function, and risk for substance abuse.

RESULTS

Of the 204 participants, 70 percent were women, 40 percent were Latino, 45 percent were Caucasian, and 14 percent were African-American. The mean and median age were 55 years old, and age ranged from 19 to 90. Half of the patient sample used opioid medication to control their CLBP. Among opioid users, prescriptions ranged from 10 mg per day in morphine equivalence to 320 mg per day, with 79 percent of dosages being less than 50 mg per day (Figure 1). On the other hand, 90 percent of opioid users took less than 115 mg per day. The median doses of moderate and high users were 30 mg per day and 180 mg per day, respectively.

Three groups of CLBP patients (high users, moderate users, and non-users of opioid medication) were compared across several dimensions, including health care utilization, comorbidities, use of other treatments for pain, and demographic characteristics. Significant group differences were evident, such that high users were more likely than moderate and non-users to have hepatitis C, to use benzodiazepines, and to be receiving treatment for depression (Table 2). The average pain scale of patients on and off medication also differed significantly between groups, and high-dose users reported the worst physical and role functioning (Figure 2). In addition, high users were significantly more likely than moderate and non-users to seek care in pain clinics, but not to attend physical therapy (Figure 3). The three groups of CLBP patients did not differ significantly with respect to their gender, ethnicity, age, or body mass index.

DISCUSSION

In this study, most opioid-using patients (90 percent) took less than 115 mg per day in morphine equivalence. The median dosage of high users, or patients taking the top 10 percent of dosages, was extraordinarily higher (500 percent) than that of the moderate users. High users were also more likely than moderate and non-users to have Hepatitis C, to seek care in a pain clinic, to use benzodiazepines, and to be receiving treatment for depression, but less likely to pursue physical therapy as a means to gain pain relief. On the other hand, 79 percent of opioid-using participants took 50 mg or less per day. These patients reported greater physical and role functioning than high users.

Such findings are consistent with previous research, which suggests that chronic, high-dose opioid use increases a patient’s pain sensitivity (OIH) and imparts poorer functionality.(3,4,11,15,16) Therefore, it may be that when patients reach extremely high dosages of prescribed opioids, it is no longer their original pain that is primarily being treated, but rather their OIH, tolerance, and/or addiction. Indeed, previous research has failed to correlate reported pain intensity with opioid use in CLBP populations and mixed chronic pain populations.(17,18,19) In addition, studies show that patients tapered off of opioids in structured pain management programs experience decreased CLBP and improved mood and functional status.(4,20)

This study allows physicians treating CLBP to compare their opioid prescribing to that of doctors in several Texas cities. While limited by a small sample of very high-dose users, this study supports the existing literature that suggests a need for tighter restriction of opioid prescribing. A second limitation is related to the research design, a prospective cohort study. Our data are observational and descriptive, intended to follow the natural history of CLBP and its treatment over time. The design does not allow us to determine cause and effect.

Although opioids have been shown to relieve pain and improve functionality of patients over a short term, the efficacy of opioid treatment long term for chronic non-cancer pain is questionable.(21,22,23,24) Many sources recommend setting stricter guidelines for prescribers and using treatments less detrimental to functional outcomes of patients.(2,10,11,21) However, the use of opioids by primary care physicians continues to grow. Because opioid-seeking patients often complain of CLBP in order to gain access to opioid prescriptions, clinicians should pay close attention to current guidelines, which describe the patient characteristics known to be risk factors for opioid abuse or diversion. Such factors include personal or family history of alcohol or drug abuse, history of mental health problems, history of arrest/legal problems, and relatively younger age.(7,8,9) Indeed, the characteristics that distinguish high users in this study correspond to those same characteristics previously shown to be predictive of prescription abuse.

The results of this study are consistent with those of prior studies that have suggested that there is an opioid dose beyond which patients might suffer decreased functionality and quality of life. We recommend that clinicians reconsider the appropriateness of opioid prescribing above 115 mg per day and closely monitor patients identified to have risk factors for abuse. We also point out that a dosage of 50 mg or less per day in morphine equivalence represents one community standard for the treatment of chronic non-cancer pain.

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Acknowledgements: Co-investigators from the Residency Research Network of Texas (RRNeT) include: Tamara Armstrong, Psy.C.; Jose Hinojosa, M.D.; Sarah Holder, D.O.; Sunand Kallumadanda, M.D.; Jerry Kizerian, Ph.D.; Shashi Mittal, M.D.; Shannon Moss, Ph.D.; Raji Nair, M.D.; Jesus Naranjo, M.D.; Darryl White, M.D.; John Whitham, D.O.; Richard Young, M.D.; and Robert Wood, Dr.P.H.

This study was funded in part by a research grant from the TAFP Foundation. Support for TAFP Foundation Research is made possible by the Family Medicine Research Champions.

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