Results from this study demonstrate increases in mean cumulative yearly dose and days supply of opioids between 2000 and 2005 for each of the four common non-cancer pain types, and with increasing number of pain diagnoses. Increasing rates of use and days supplied were seen in all the NCP conditions tracked, and there was no evidence of differential rates of increase by pain type. Whereas rates of opioid use did not differ widely between non-cancer pain conditions, long-term opioid use rates doubled with each additional pain diagnosis. Dose increases were most marked for short-acting schedule II agents for all pain types and number. In contrast, mean cumulative yearly opioid dose of schedule III-IV opioids remained relatively stable between 2000 and 2005. This growth in use of the more potent Schedule II opioids, and for longer duration, likely reflects increased attention to the problem of inadequately treated pain in addition to changing clinical attitudes concerning the use of potent opioids for non-cancer pain.
While the majority of the population of NCP patients receiving opioids in both insurers had only one pain diagnosis (most commonly arthritis/joint pain), the percent with multiple pain diagnoses increased between 2000 and 2005. In addition, differences in opioid use varied more by number of pain diagnoses than by pain types. Hence, trends in opioid prescribing by pain type likely reflect the degree of comorbidity (i.e., number of pain diagnoses) within each pain type. The pain type with the lowest mean cumulative opioid dose and days supply (arthritis/joint pain) was also the pain type most likely to occur without additional comorbid pain diagnoses. Similarly, those with neck pain had the highest mean number of pain conditions, and also had the greatest increases in dose and percent with >90 days supply. The highest levels, and greatest percent increases, in mean cumulative opioid dose and days supply occurred for the most part among those with back or neck pain, and with three or four pain diagnoses. Mean opioid dose per day supply and percent with daily dose >120mg morphine equivalents, however, did not change much between 2000 and 2005. Hence, as with the overall trends previously reported30
, increases in cumulative yearly dose were driven by an increase in days supply, not the amount prescribed per day. The percent of enrollees with NCP diagnoses and the percent with any opioid use increased between 2000 and 2005, but at a lower rate than the increases observed in long-term opioid use (>90 days supply) and mean days supply during the same years. This suggests that rates of opioid initiation are not increasing as fast as rates of opioid continuation within the group of NCP patients already on opioids.
The trends observed in this study suggest an increased tendency to prescribe long-term opioid therapy, especially to those patients with multiple pain conditions. It is not possible from these analyses to determine the exact reasons for the trends observed, but some speculations can be made based on prior research. The mean cumulative opioid dose and days supplied in both insurers increased with increasing number of pain diagnoses, possibly reflecting greater pain intensity or activity interference. Individuals with multiple pain site may be more likely to have an inadequate response to non-opioid pain treatments36
. Multiple pain conditions have also been shown to be more strongly associated with psychopathology than single pain conditions,11
and the presence of a comorbid mental disorder may predict opioid use among individuals with chronic pain.33
The higher rates of opioid use, days supply and dose in the Arkansas Medicaid sample likely reflects the greater disability and disease burden of this population.33, 34
It is also possible that this disadvantaged population has less access to non-opioid rehabilitative therapies (e.g., physical therapy) for NCP compared to privately insured individuals.12
This observed difference between the two insurers appears to be general, and not specific, to certain pain types or number.
The higher rates of opioid use found in this study for enrollees with back pain compared to those with arthritis/joint pain are consistent with data from the population-based Healthcare for Communities Survey.32, 33
Treatment guidelines for low back pain recommend opioid analgesics for those who have severe, disabling pain that is not controlled with acetaminophen and NSAIDs.2, 8
None of the randomized trials evaluating the use of opioids for back pain, however, have examined long-term use.10, 19, 35
Continued pain relief with treatment longer than six months has been reported for some in open label, uncontrolled studies, but dropout rates have been high21, 23
. The increases in mean days supply and percent with >90days observed in our study suggest that these opioids are being prescribed on an increasingly long-term basis. While the current research base on use of opioids for NCP is insufficient to recommend one opioid over another,10, 19
the use of longer-acting agents has been recommended for pain that is frequent or constant.4
Our data, however, show only a modest increase over time in mean cumulative yearly of long-acting agents compared to larger increases for short-acting agents.
While those with arthritis/joint pain had a lower absolute mean cumulative yearly opioid dose and days supply, dose and days supply still increased over time. Traditionally, opioids have been recommended as an alternative for osteoarthritis after acetaminophen, and if non-steriodal anti-inflammatory agents (NSAIDs; including COX-2 selective inhibitors) were contraindicated, ineffective or poorly tolerated.27
Acetaminophen and NSAIDs have similarly been recommended as first-line agents for treatment of back pain. Since 2004-2005, however, NSAID recommendations have been shifted towards short-term use due to cardiovascular and gastrointestinal safety concerns, making the use of opioids more accepted in these populations. Nevertheless, we observed increasing trends in opioid use long before this change in guidelines, suggesting there are other factors that account for the increase. The analyses in this study were limited to opioid use trends, and did not include information on other medications used to treat pain and treatment responsiveness. Hence, it is not possible to determine whether opioids were used as an alternative to NSAIDS in accord with guideline recommendations.
The percent of opioid users with headaches in this study was small, consistent with the range of 4-28% reported in prior studies.1, 24
Rates of use increased between 2000 and 2005, although less than for the other pain conditions. The majority of those with headaches and opioid use had multiple pain diagnoses, and thus it is likely that in some cases, opioids were targeted more towards other pain diagnoses. Headache is a very diverse diagnostic category, ranging from mild tension headache, to intermittent but severe migraine attacks, to chronic daily headache. Recommendations regarding the use of opioids for headache are generally limited to treatment of acute migraine attacks that do not respond to first-line agents.20
Daily scheduled opioids may provide some benefit for a small number of those with chronic daily headache,26
however in general, chronic use is controversial due to concerns about the risk of medication overuse headache with overuse of narcotic analgesics.18, 25, 39
There are several limitations to our study. The identification of pain types in our study was based on mention of diagnoses in administrative claims records, and lacks detail on frequency, severity or duration of symptoms. Some of those we identified as having a NCP diagnosis may have had pain that was relatively short-term (e.g., back pain following an acute injury with full recovery) or that is relatively infrequent or managed with prophylactic medication (e.g., migraine headaches). However, given that nearly three fourths of the samples from both insurers had arthritis/joint pain, and most of those with the other pain types had at least one other pain diagnosis, symptoms are likely to be chronic or recurrent for a large percentage of the enrollees identified as having NCP. We did not link the opioid prescriptions more directly to the diagnoses other than determining they were prescribed in the same year. Hence, it is possible some of the opioids were prescribed for conditions other than those examined here. The data presented in this analysis focused on descriptive data of trends over time, and did not include information on other variables that may influence opioid dosing or duration such as medical and psychiatric comorbidities and other concurrent pain treatments. In future TROUP analyses, we plan to examine the relationships between socio-demographic, medical and psychiatric factors and opioid use.
In summary, results from this study demonstrate increases between 2000 and 2005 in NCP diagnosis rates and percent with each diagnosis prescribed acute or chronic opioids. There were also increases observed in mean cumulative dose and day supply of opioids in both a private and publicly insured population, most notable for those with multiple pain diagnoses and/or neck pain. Further research is warranted to determine the long term benefits and risks to patients with multiple pain conditions associated with long-term opioid use.