Low back pain causes 2.4% of visits to US emergency departments (ED) resulting in 2.7 million visits annually. In a general low back pain (LBP) population, prognosis is poor. About 50% of patients who visited general practitioners with new onset musculoskeletal LBP report persistent pain and functional disability three months after the index visit. Outcomes are similarly poor for the population of patients forced to use an ED for management of their LBP. In an observational study of patients with non-traumatic LBP recently completed at the PI's institution, patients were contacted one week after ED discharge: 70% reported persistent back-pain related functional impairment, 59% reported moderate or severe LBP, and 69% reported analgesic use within the previous 24 hours. Three months after the ED visit, 48% reported functional impairment, 42% reported moderate or severe pain, and 46% reported analgesic use within the previous 24 hours.

A variety of evidence-based medications are available to treat LBP. Non-steroidal anti-inflammatory drugs (NSAID) are more efficacious than placebo with regard to pain relief, global improvement, and requirement of analgesic medication. Skeletal muscle-relaxants too are effective for short-term pain relief and global efficacy. Opioids are commonly used for moderate or severe acute LBP,(9) though high-quality evidence supporting this practice is lacking.

Treatment of LBP with multiple concurrent medications is common in the ED setting. Emergency physicians often prescribe NSAIDs, skeletal muscle relaxants, and opioids in combination. Several clinical trials have compared combination therapy with NSAIDS+ skeletal muscle relaxants to monotherapy with just one of these agents. These trials have reported heterogeneous results. The combination of opioids + NSAIDS has not been evaluated experimentally in patients with acute LBP.

Given the poor pain and functional outcomes that persist beyond an ED visit for musculoskeletal LBP, the investigators propose a clinical trial to evaluate whether combining muscle relaxants or opioids with NSAIDs is more effective than NSAID monotherapy for the treatment of non-traumatic, non-radicular low back pain. Specifically, the investigators will evaluate three distinct hypotheses:

1. The combination of naproxen + cyclobenzaprine will provide greater relief of LBP than naproxen alone seven days after an ED visit, as measured by the Roland Morris low back pain functional disability scale
2. The combination of naproxen + oxycodone/ acetaminophen will provide greater relief of LBP than naproxen alone seven days after an ED visit, as measured by the Roland Morris low back pain functional disability scale
3. The combination of naproxen + oxycodone/ acetaminophen will provide greater relief of LBP than naproxen + cyclobenzaprine seven days after an ED visit, as measured by the Roland Morris low back pain functional disability scale

Inclusion Criteria:

• Non-radicular, non-traumatic low back pain of no more than 2 weeks duration

Exclusion Criteria:

• Back pain longer than 2 weeks
• Prior to the acute attack of low back pain, back pain once per month or more frequently
• Prior to the acute attack of low back pain, daily or near daily use of pain medication

Patients enrolled and randomized