Is baclofen (a muscle relaxant) effective for treating chronic back pain in adults with a history of muscle spasms or spasticity?

Baclofen for Back Pain

Baclofen is not recommended for chronic back pain in adults, as it lacks evidence of efficacy for this indication and is specifically not FDA-approved for skeletal muscle spasm from rheumatic disorders. 1

FDA-Approved Indications vs. Back Pain

• Baclofen is FDA-approved only for spasticity from multiple sclerosis and spinal cord diseases, not for skeletal muscle spasm from rheumatic or mechanical back disorders 1
• The FDA label explicitly states: "Baclofen tablets are not indicated in the treatment of skeletal muscle spasm resulting from rheumatic disorders" 1
• Despite efficacy in spasticity of spinal origin (70-87% improvement in open-label studies), baclofen has sparse evidence for low back pain with only 2 trials, compared to 8 trials supporting tizanidine 2, 3

Preferred Alternative: Tizanidine

For back pain requiring muscle relaxant therapy, tizanidine is the evidence-based choice, not baclofen. 2

• The American College of Physicians recommends tizanidine as the preferred muscle relaxant for lumbar radiculopathy due to superior efficacy and safety profile 2
• Tizanidine demonstrated efficacy in 8 clinical trials for acute low back pain, while baclofen has minimal evidence in this population 2
• Starting dose: 2-4 mg daily (2 mg in older adults), titrated upward as needed 2
• Combination therapy: Adding tizanidine to NSAIDs or acetaminophen provides consistently greater short-term pain relief than monotherapy 2

Why Baclofen Is Not Appropriate for Back Pain

• Muscle relaxants like baclofen do not actually relax skeletal muscle directly; their effects are nonspecific and likely related to sedative properties 4
• If true muscle spasm from spinal origin is suspected (not typical mechanical back pain), baclofen may be considered, but only as a second-line option 4
• Baclofen's primary role is for spasticity with velocity-dependent hyperactivity of stretch reflexes, not the muscle tension associated with mechanical back pain 4

Safety Considerations

• All muscle relaxants increase CNS adverse events 2-fold (sedation, dizziness, weakness) compared to placebo 2
• Baclofen carries specific risks: sedation (10-75% incidence), excessive weakness, vertigo, and psychological disturbances 3
• Critical withdrawal risk: Abrupt discontinuation can cause seizures, psychic symptoms, and hyperthermia; requires slow tapering 4, 3
• Higher risk in elderly patients and those with renal disease, where baclofen may accumulate 3
• Treatment duration should be limited to 7-14 days maximum for acute pain conditions 2

Clinical Algorithm for Back Pain

1. First-line for radiculopathy: Gabapentin, which has demonstrated small, short-term benefits specifically in radiculopathy 2
2. Muscle relaxant if needed: Tizanidine 2-4 mg daily, titrated as tolerated, combined with NSAIDs or acetaminophen 2
3. Avoid: Baclofen for mechanical back pain, cyclobenzaprine (limited evidence), and benzodiazepines (abuse potential, no proven efficacy) 4, 2
4. Monitor: Sedation with all muscle relaxants; hepatotoxicity specifically with tizanidine 2
5. Reassess: If no improvement after time-limited course, reconsider diagnosis rather than continuing ineffective therapy 2

Special Populations

• Older adults: Start tizanidine at 2 mg to minimize falls risk and CNS effects; avoid baclofen due to higher adverse effect burden 4, 2
• Renal impairment: Both baclofen and tizanidine require dose adjustment; baclofen carries unnecessarily high risk in renal disease 2, 3
• Chronic pain: No muscle relaxants, including baclofen, have evidence of efficacy in chronic pain conditions 4