When should a patient with acute lower back pain treated with a short course of dexamethasone (Decadron) and cyclobenzaprine (Flexeril) seek urgent medical evaluation or follow‑up?

When to Seek Further Evaluation After Lower Back Pain Treatment with Flexeril and Decadron

Immediate Emergency Department Return (Within 24–48 Hours)

Return immediately if you develop any "red flag" symptoms that suggest serious underlying pathology requiring urgent imaging or specialist evaluation.

• New or worsening leg weakness — inability to stand on toes, walk on heels, or lift your foot (foot drop) suggests nerve compression requiring urgent evaluation 1
• Loss of bowel or bladder control — new urinary retention, inability to urinate, or loss of bowel control indicates cauda equina syndrome, a surgical emergency 1
• Saddle anesthesia — numbness in the groin, inner thighs, or around the rectum suggests severe nerve compression 1
• Severe or progressive leg pain that is worse than your back pain, especially if it radiates below the knee, may indicate worsening nerve root compression 1
• Fever with back pain — temperature >100.4°F (38°C) raises concern for spinal infection (discitis, epidural abscess) 1
• Unrelenting pain at rest or night pain that wakes you from sleep and is not relieved by position changes may indicate tumor or infection 1

Follow-Up Within 1 Week

Schedule a follow-up visit if your pain has not improved meaningfully after 3–4 days of treatment, because the steroid injection (Decadron) should provide relief within this timeframe if it is going to work.

• No improvement in pain or function after 3–4 days — systemic corticosteroids like Decadron are ineffective for most low back pain with or without sciatica, so lack of response by day 3–4 suggests the injection provided no benefit and alternative treatments are needed 1
• Worsening pain despite medication — if pain intensity increases or functional impairment worsens while taking Flexeril (cyclobenzaprine), reassessment is necessary 1
• Intolerable side effects from Flexeril — excessive drowsiness, dizziness, dry mouth, or sedation that interferes with daily activities or driving warrants medication adjustment 1, 2

Follow-Up Within 2–4 Weeks

Return for reassessment if pain persists beyond 2 weeks, because acute low back pain typically improves rapidly in the first month, and failure to improve suggests the need for treatment escalation.

• Persistent moderate-to-severe pain at 2 weeks — most acute low back pain resolves within 4 weeks, so ongoing significant pain requires re-evaluation and consideration of NSAIDs, physical therapy, or other interventions 1
• Inability to return to normal activities — if you cannot perform usual work or daily tasks after 2 weeks of treatment, additional therapies are indicated 1
• Pain radiating into the leg (sciatica) that does not improve within 2–4 weeks may benefit from gabapentin or other neuropathic pain medications 3

Important Medication Caveats

Understand that both medications you received have significant limitations, and you should not expect prolonged benefit from either one.

• Decadron (dexamethasone) is not effective for low back pain — multiple high-quality trials consistently show systemic corticosteroids provide no clinically significant benefit for acute low back pain with or without sciatica compared to placebo 1
• Flexeril (cyclobenzaprine) works only for the first 3–7 days — all trials of muscle relaxants were ≤2 weeks duration, with greatest effect in the first 4 days, so do not continue this medication beyond 1–2 weeks 1, 4
• Flexeril causes drowsiness in most patients — avoid driving or operating machinery until you know how this medication affects you, and do not combine with alcohol or other sedating medications 1, 2
• Flexeril does not work better when combined with NSAIDs — a 2015 JAMA trial found that adding cyclobenzaprine to naproxen provided no additional benefit over naproxen alone for functional outcomes or pain at 1 week 5

What to Expect and When to Escalate

Most acute low back pain improves within 4 weeks, but up to one-third of patients report persistent pain at 1 year, so early identification of non-responders is critical.

• If pain is not improving by day 7, contact your provider to discuss adding an NSAID (ibuprofen 600–800 mg three times daily or naproxen 500 mg twice daily) as first-line therapy, which has moderate evidence for short-term pain relief 1
• If pain persists beyond 4 weeks, you have transitioned to subacute low back pain and should be evaluated for physical therapy, exercise programs, or consideration of imaging if not already performed 1
• If pain becomes chronic (>12 weeks), muscle relaxants are no longer appropriate, and treatment should shift to tricyclic antidepressants (e.g., amitriptyline), duloxetine, or gabapentin for neuropathic pain 1, 3

Specific Monitoring for Decadron Side Effects

Although you received only a single injection or short course, be aware of potential corticosteroid adverse effects that warrant medical attention.

• Elevated blood sugar — if you have diabetes, monitor glucose closely for 3–5 days after the injection, as even a single dose can cause transient hyperglycemia 1
• Insomnia or nervousness — corticosteroids commonly cause sleep disturbance and agitation, which typically resolve within a few days 1
• Increased appetite — expect temporary increase in hunger for 2–3 days after the injection 1