Muscle Relaxants for Hamstring Pain
Muscle relaxants are not recommended for hamstring pain, as they lack evidence of efficacy for peripheral musculoskeletal injuries and carry significant risks of sedation and falls, particularly in older adults. 1
Why Muscle Relaxants Are Not Appropriate for Hamstring Injuries
Most muscle relaxants do not directly relax skeletal muscle and have no evidence of efficacy in chronic pain or peripheral muscle injuries—they work primarily through sedative properties rather than targeting the actual muscle pathology 1, 2
The American Geriatrics Society explicitly states that muscle relaxants should only be used when true muscle spasm or spasticity from central nervous system injury is suspected, not for peripheral musculoskeletal conditions like hamstring strains 1
Cyclobenzaprine, the most commonly prescribed muscle relaxant, has been studied primarily for acute low back pain and neck pain, not for extremity muscle injuries like hamstring strains 3, 4
Evidence-Based Treatment for Hamstring Pain
First-line pharmacologic treatment should be oral NSAIDs (such as ibuprofen or naproxen) or acetaminophen, which have moderate-certainty evidence for reducing pain in acute muscle sprains: 5
NSAIDs can reduce pain by approximately 0.93 cm on a 10-cm visual analog scale within 2 hours in patients with acute muscle sprains 5
Acetaminophen can reduce pain by approximately 1.03 cm on a 10-cm scale within 2 hours 5
The American College of Physicians and American Academy of Family Physicians recommend oral NSAIDs as first-line therapy for acute muscle sprains based on moderate-certainty evidence 5
Why Cyclobenzaprine Specifically Should Be Avoided
Cyclobenzaprine has only been studied in back and neck pain, not extremity injuries—the evidence base does not support extrapolating its use to hamstring injuries 3, 4, 6
Even in back pain where it has been studied, cyclobenzaprine shows only modest benefit with an effect size of 0.38 to 0.58, and the effect is greatest only in the first 4 days of treatment 4
The most common adverse effect is drowsiness, occurring in over 50% of patients taking cyclobenzaprine 5-10 mg compared to 35% with placebo 3
The American Geriatrics Society lists cyclobenzaprine in the Beers Criteria as potentially inappropriate for older adults due to its structural similarity to tricyclic antidepressants with comparable adverse effects including CNS impairment, delirium, and increased fall risk 1
Critical Clinical Pitfalls to Avoid
Do not prescribe muscle relaxants believing they will directly relieve muscle spasm in a hamstring injury—this is a fundamental misunderstanding of how these medications work 1, 2
Avoid combining muscle relaxants with opioids, as this increases mortality risk 3- to 10-fold compared to opioids alone, and the FDA has issued a black box warning against this combination 7
Do not use muscle relaxants in elderly patients, frail patients with mobility deficits, or those at risk for falls 1
When Muscle Relaxants Might Be Considered (Not for Hamstring Pain)
Muscle relaxants like baclofen or tizanidine are appropriate only for: 1, 2
- True spasticity from upper motor neuron syndromes (stroke, spinal cord injury, multiple sclerosis)
- Acute low back pain or neck pain (not extremity injuries) when NSAIDs alone are insufficient
- Time-limited courses of 7-14 days maximum for acute conditions 2