Evidence based

Baclofen vs. Flexeril: Choosing the Best Option for Your Muscle Pain and Spasms

Last updated: 
April 1, 2020
Dr. Julieann Berg, DPT
Researcher and author, Physical Therapist

Lower back pain accounts for twenty percent of physician visits in the US (1). Back pain and related musculoskeletal disorders can interfere with daily routines, sleep, job performance, and your ability to enjoy your hobbies.

Conservative treatment, such as physical therapy, exercise, and nonsteroidal anti-inflammatory drugs (NSAIDs), should always be the first line of treatment for muscle spasm and related pain. However, more severe cases, these primary treatments may prove insufficient. For persistent pain, your primary care physician may recommend muscle relaxants.

In this article, we’ll explore how muscle relaxants work, compare two specific relaxants (cyclobenzaprine, sold under the brand Flexeril, versus baclofen), and offer advice for how to decide which one would be better for your pain.

How Muscle Relaxants Work

Skeletal muscle relaxants can work on the central nervous system (CNS) or the peripheral nervous system (PNS), depending on the underlying cause of the muscle spasm and the patient’s medical condition. The central nervous system primarily consists of the brain and spinal cord. The peripheral nervous system primarily consists of specific nerves and skeletal muscles throughout the body.

The underlying cause of your muscle pain has implications for the efficacy of different types of muscle relaxants. There are two classes of relaxants to choose from: Antispastics and antispasmodics.

Antispastic drugs work at the spinal cord or on specific muscles to reduce muscle tone and involuntary movement. As the name suggests, they treat spasticity, a muscle’s resistance to movement that’s dependent on the speed of movement. Spasticity commonly results from injury to the central nervous system. Examples of conditions involving muscle spasticity include cerebral palsy, multiple sclerosis, and spinal cord injury (1). Baclofen is a common antispastic prescribed to treat these conditions.

By contrast, antispasmodic drugs alter signal conduction in the central nervous system, consequently limiting muscle spasms throughout the entire body. These drugs can act on the brain, the brain stem, or the spinal cord. Cyclobenzaprine, sold under the brand name Flexeril, is a common antispasmodic drug typically prescribed for acute pain (1).

Antispasmodic and antispastic drugs aren’t interchangeable for muscle pain treatment, although a handful of drugs (such as tizanidine and diazepam) can exhibit both antispastic and antispasmodic properties (1).


Muscle relaxants can act on the central nervous system or on the peripheral nervous system, depending on the cause of the muscle spasm. They’re generally classified as antispastic drugs or antispasmodic drugs, depending on their mechanism of action.

Baclofen: How It Works and When to Use It

Mechanism of Action

Baclofen is an FDA-approved, antispastic medication used to treat chronic musculoskeletal pain related to spasticity (2). It’s particularly useful for flexor muscle spasms (e.g., hip flexors, hamstrings), clonus (involuntary, rhythmic muscle spasms caused by a lesion in the brain), and associated pain (3). These symptoms can be associated with a spinal cord injury or multiple sclerosis, among other neurological disorders (2).


Baclofen can be administered orally or intrathecally through a surgically inserted spinal cord pump. Intrathecal baclofen is generally considered if a patient demonstrates adverse effects or no response to oral delivery (2).

Baclofen dissipates rapidly after administration (due to its short half-life), and so must be administered every 2 - 6 hours for optimal effect. People who use baclofen often require dosage increases over time to maintain the same therapeutic effects (2). Your doctor will help you determine the right dose for your particular case.


Research shows that baclofen is an effective treatment for muscle spasm related to spasticity, especially in people with multiple sclerosis, spinal cord injury, and children over 12 with cerebral palsy (1, 2, 4, 5). Intrathecal baclofen is FDA-approved for people with moderate to severe spasticity due to traumatic brain injury, spinal cord injury, or other CNS lesion (2, 6).

The research regarding the efficacy of baclofen for the treatment of common musculoskeletal conditions, such as back pain, is limited (2, 4). One study found that patients with acute lower back pain treated with ibuprofen (NSAID) alone had similar pain and function levels to patients treated with baclofen and ibuprofen (7).


Baclofen is an antispastic drug used to treat chronic pain related to muscle spasticity and is delivered through an oral tablet or an intrathecal pump. Research supports the use of baclofen in patients with multiple sclerosis, spinal cord injury, or brain injury, but not nearly as strongly in cases of back pain.

Cyclobenzaprine: How It Works and When to Use It

Mechanism of Action

Cyclobenzaprine (sometimes branded as Flexeril) is an antispasmodic, FDA-approved medication for the treatment of acute musculoskeletal pain (8). It belongs to a group of medications called tricyclic antidepressants. Cyclobenzaprine should be combined with rest and other conservative interventions in the treatment of acute muscle spasm.

Cyclobenzaprine functions as a depressant and sedative agent for the central nervous system, specifically acting on the spinal cord and reducing muscle hyperactivity (8). Muscles are innervated (stimulated to action) by nerves from the spinal cord, and cyclobenzaprine dulls the signals sent out by these nerves. By inhibiting these signals, cyclobenzaprine reduces or even eliminates muscle spasms.

Other antispasmodic agents include carisoprodol, metaxalone, methocarbamol, orphenadrine, and chlorzoxazone (1).


Cyclobenzaprine (Flexeril) is delivered orally in immediate-release capsules (generally 5 - 10 mg) or extended-release capsules (generally 15 - 30 mg) (8). Daily dosage exceeding 30 milligrams isn’t recommended, and clinical studies completed to date suggest that small dosages (5 milligrams) are most effective (8, 9). This drug is recommended for short-term use (two or three weeks) and current research doesn’t support prolonged use (10).


The evidence suggests that cyclobenzaprine is an effective treatment for musculoskeletal conditions and outperforms placebos, especially in patients with acute lower back or neck pain (1, 4). Short duration studies show that cyclobenzaprine is also effective in reducing pain from fibromyalgia (10). Cyclobenzaprine has been used in more clinical trials than other antispasmodic drug and consistently relieves pain (4).

Use this drug on a short-term basis for acute pain relief. Long-term usage could mask the underlying cause of the pain (1).


Cyclobenzaprine (Flexeril) is an antispasmodic drug used to treat musculoskeletal pain related to acute injury. Research supports the use of cyclobenzaprine in patients with acute lower back pain, acute neck pain, and fibromyalgia.

Risks of Baclofen and Flexeril

Side Effects

The most common adverse effects of cyclobenzaprine are drowsiness, dry mouth, dizziness, and confusion (8). Additional potential side effects of this drug include fatigue, headache, nervousness, dilated pupils, hallucinations, increased heart rate, and digestion issues (1, 8).

The most common side effects of baclofen are muscle weakness, confusion, vertigo, nausea, and momentary sedation or drowsiness (2, 4, 11). Additional potential side effects of this drug include low blood pressure, swelling, shortness of breath, and insomnia among many other reported adverse effects (2). These side effects are most common with oral baclofen and less common with intrathecal baclofen because the drug is injected directly into the fluid surrounding the brain and spinal cord (11).

The intrathecal administration of baclofen must be monitored closely by the medical team and patient to ensure the pump is working properly (2). Any issues with the delivery system can induce withdrawal from the drug in patients who have been using baclofen for more than two months (2). Baclofen withdrawal can be life-threatening with possible multi-organ failure and psychological symptoms (2, 12).

When you want to cease a course of baclofen, you should talk to your doctor to come up with a gradual dose reduction schedule to help avoid withdrawal symptoms associated with discontinuation (2).


Cyclobenzaprine was originally intended for use as an antidepressant (8). As such, if you’re on other antidepressants while taking cyclobenzaprine, your doctor should closely monitor your treatment course (8). You shouldn’t use cyclobenzaprine if you have hyperthyroidism, arrhythmias, heart failure, heart conduction issues, or are recovering from a heart attack (8). Don’t drive or operate heavy machinery while taking cyclobenzaprine (8).

Use baclofen cautiously if you have kidney issues (2, 13). Additionally, if you’re pregnant or nursing, you should use baclofen only if the perceived benefits of the drug outweigh the risks to the fetus or infant (2). Don’t opt for an excessively long treatment duration with baclofen, as you might find yourself dealing with life-threatening withdrawal symptoms as you try to wind down the treatment.

In general, avoid combining baclofen or cyclobenzaprine with any prescription drug that acts on the central nervous system (2, 8). Don’t take either medication with sedatives or alcohol (8).


Both baclofen and cyclobenzaprine carry significant adverse effects, and you should seek professional medical advice to determine which is best for you. Be aware of contraindications and drug interactions when taking these medications.

Deciding on the Best Option for You

Conservative treatment, such as physical therapy, exercise, and NSAIDs, should always be the first choice for remedying muscle spasms and related pain. Most healthcare professionals agree that muscle relaxants are overprescribed, especially since the risks and adverse effects outweigh the benefits in some cases (1).

If you’re experiencing acute back or neck pain as a result of musculoskeletal injury or fibromyalgia, then cyclobenzaprine is your best option.

If you’re dealing with spasticity and chronic pain related to neurological disease or injury, such as multiple sclerosis or spinal cord injury, then baclofen may be best for you.

Always discuss your medical history with your healthcare provider to determine which medication is safest for you to take. Be aware of possible adverse effects and contraindications related to your personal history. Discuss dosing and delivery options with your healthcare provider to minimize risks.

The perceived benefits of taking any medication should always outweigh the potential risks.


Conservative treatment is the first line of treatment with all muscle spasm. Cyclobenzaprine may help with acute musculoskeletal pain, while baclofen may help relieve chronic pain and spasticity due to a neurological origin. Your medical history will help determine the safest medication for you.


Both baclofen and Flexeril (cyclobenzaprine) are skeletal muscle relaxants that work in different ways to relieve muscle spasm. Both carry significant adverse effects and should only be used for short-term treatment.

Generally, cyclobenzaprine is more effective in treating acute musculoskeletal pain due to an injury in the back or neck. Chronic pain from muscle spasticity related to neurological disease or injury responds best to baclofen.

Talk to your healthcare provider in-depth about your medical history to determine the safest medication for relieving your muscle spasm and pain.

The information provided in this article is not a substitute for professional medical advice, diagnosis, or treatment. You should not rely upon the content provided in this article for specific medical advice. If you have any questions or concerns, please talk to your doctor.

Research Citations

Researched, written, and reviewed by:
Dr. Julieann Berg, DPT
Researcher and author, Physical Therapist
Julieann is a physical therapist who specializes in pediatric care. She holds a Doctorate of Physical Therapy from Columbia University, where she graduated with honors, and enjoys yoga, dancing, and following Philadelphia sports.
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