BACKGROUND

Low back pain is a common ED presentation, resulting in 2.3% of all ED visitsReference Friedman, Chilstrom and Bijur ¹ . Pain outcomes and quality of life after presentations for low back pain are generally poor, with one large study demonstrating that 70% of patients had pain-related functional impairment at one week, and 48% had continued impairment at three monthsReference Friedman, O’Mahony and Mulvey ² . Additionally, 69% reported daily analgesic use at one week, while 46% were still using analgesics at three monthsReference Friedman, O’Mahony and Mulvey ² .

There are multiple medications available to treat low back pain in the acute setting. Treatment of low back pain in the ED typically involves multiple concurrent medications, with one study demonstrating that 26% of patients received both a non-steroidal anti-inflammatory drug (NSAID) and an opioid, another 26% received an NSAID and a muscle relaxant, and 16% received all three medicationsReference Friedman, Chilstrom and Bijur ¹ . Despite the common use of these medications, the evidence for opioids in the treatment of acute low back pain is very limitedReference Deyo, Von Korff and Duhrkoop ³ . Additionally, existing data comparing the combination of NSAIDs plus muscle relaxants with NSAIDS plus placebo has been conflictingReference Berry and Hutchinson ^{4 -} Reference Pareek, Chandurkar and Chandanwale ⁸ .

OUTCOMES MEASURED

The primary outcome was improvement on the RMDQ between ED discharge and the 7-day telephone follow-up. A 5-point improvement was considered clinically significant. Additional outcomes assessed at seven days included severity of pain, frequency of medication use during the preceding 24 hours, patient satisfaction, length of time to return to normal activities, frequency of visits to any clinician, and adverse events. Patients were also contacted at three months after the ED visit to assess the change in their RMDQ.

STUDY CONCLUSION

Among patients with acute, non-traumatic, non-radicular low back pain presenting to the ED, adding cyclobenzaprine or oxycodone/acetaminophen to naproxen alone did not improve functional outcomes or pain at 1-week follow-up. These findings do not support the use of these additional medications in this setting.

COMMENTARY

Friedman et al. conducted a well-designed, randomized controlled study comparing the combination of naproxen with oxycodone/acetaminophen, cyclobenzaprine, or placebo assessing improvement in functional outcomes using a previously validated scoring tool. Based on the criteria from the Cochrane Handbook of Systematic Reviews Reference Higgins and Green ⁹ , this study was at low risk of bias with respect to random sequence generation, allocation concealment, blinding of participants and personnel, incomplete outcome data, selective reporting, and other bias. There was unclear risk of bias with regard to outcome assessment, as the authors do not state whether the research assistants performing follow-up phone calls were blinded to the treatment allocations.

Overall, the study demonstrated no significant difference in functional outcomes at seven days or three months. All of the patients had high baseline RMDQ scores, suggesting significant functional impairment at baseline. Additionally, the study demonstrated low rates of return visits to both the ED (1%-3%) and any clinician (10%-13%) among all three groups within the following week.

It is important to note that only 63% of the patients took the naproxen as prescribed. Additionally, only 62% of the patients took the study medication at least once per day, with 8% of the patients taking the medication only one time and 16% of the patients never taking the medication at all. Considering that 24% of the patients took the medication once or never, this may have affected the internal validity by blunting the effect difference between study groups. Therefore, it is possible that, if the medications were taken as prescribed, a difference may have been noted that was not identified in the study. However, this also increases the external validity, as patients are not always compliant with medications, and although having frequent reminders and phone calls to take medications may increase patient compliance, this approach is unrealistic in common practice. It is also unclear whether these patients may have stopped taking the medications early due to sufficient pain relief without recurrence after discharge. With regards to outcomes, the study’s shortest assessment was at seven days. Given that the average return to work was three days and nearly half of the patients were pain-free at seven days, it would have been valuable to know whether there was a difference in pain relief in the first three days after ED presentation, as this may suggest a benefit for a short course of these medications. Furthermore, the study only assessed one type of opioid (oxycodone) and one type of muscle relaxant (cyclobenzaprine) given at a frequency of once every eight hours. This may not apply to other opioids or muscle relaxants or different frequencies of use. For example, oxycodone is typically prescribed every four to six hours rather than every eight hours. Taking the medication every six hours may increase pain control at the risk of increased side effects. Finally, this study was performed in a select patient population with atraumatic back pain without radicular symptoms within an urban population with typically poor follow-up. Therefore, this may not be applicable to all populations.

Of equal importance, this study also identified increased adverse effects within the cyclobenzaprine and oxycodone/acetaminophen groups, with drowsiness, dizziness, and nausea or vomiting being the most significant. While the clinical significance of these events may depend upon the individual patient, it is important to discuss potential adverse events with patients, as the number needed to harm ranged from 5.3 (95% CI =3 to 14) to 7.8 (95% CI =4 to 129).

Finally, approximately 24% of the patients still had moderate or severe low back pain at 3-month follow-up, suggesting that a number of patients will have prolonged pain irrespective of the acute medication given. In these patients, encouraging activity and ensuring primary care follow-up may be the most important ED interventionsReference Hagen, Jamtvedt and Hilde ¹⁰ .