Many people experience muscle cramps (spasms) every now and then. Muscle spasms typically occur when we overuse or injure our muscles. While these cramps can be painful, they usually last for only a few seconds or minutes.
But for some people, muscle spasms are frequent and intensely painful. The spasms can also last for long periods of time. When a spasm hits, severe symptoms can negatively impact your quality of life.
Fortunately, medications are available that can help relieve your symptoms. Two common muscle relaxer medications are baclofen and cyclobenzaprine (Flexeril). They’re routinely filled at pharmacies across the country with a similar treatment goal in mind, but they’re given for different reasons.
Here, we’ll compare baclofen and cyclobenzaprine — what they are, how effective they are, and what side effects to expect.
What is baclofen?
Baclofen is a prescription medication that’s usually taken by mouth. It can also be given as a spinal injection (Gablofen).
Baclofen is considered to be an antispastic muscle relaxant or a spasmolytic, which is used to treat muscle spasms due to brain injury or nerve damage.
What is baclofen approved to treat?
Antispastic muscle relaxants — like baclofen — are used for muscle spasticity conditions. For these conditions, people have unusually tight, stiff, and rigid muscles that repeatedly spasm because of brain injury or nerve damage.
In fact, the FDA approved baclofen to treat muscle spasticity symptoms caused by spinal injuries or spine-related medical conditions. The FDA also approved baclofen to relieve similar symptoms in people with multiple sclerosis (MS), a type of autoimmune disorder.
How does baclofen work for muscle spasms?
Baclofen is thought to work by affecting the spinal nerves. It lessens the number and severity of muscle spasms. It also relieves pain, loosens rigid muscles, and helps with muscle movement.
What is cyclobenzaprine?
Like baclofen, cyclobenzaprine is a prescription medication that’s taken by mouth. But unlike baclofen, cyclobenzaprine is an antispasmodic muscle relaxant. This means it’s used to treat muscle spasms due to muscle and bone problems.
What is cyclobenzaprine approved to treat?
Cyclobenzaprine is routinely used to treat muscle spasms caused by musculoskeletal conditions. These are muscle spasms related to problems from the muscles and bones — not the brain or spine.
These types of muscle spasms can also be painful. But the pain is usually acute (short-term), not chronic. So, the FDA only approved cyclobenzaprine use for 2 to 3 weeks at a time to relieve painful muscle spasms from these musculoskeletal conditions. Cyclobenzaprine should also be used in combination with rest and physical therapy when possible.
How does cyclobenzaprine work for muscle spasms?
Cyclobenzaprine is thought to relax muscles by mainly working in the brain. To a lesser extent, it also exerts its effects on the spine. It doesn’t work by affecting muscles directly.
How are baclofen and cyclobenzaprine dosed and given?
The following table contains information on how baclofen and cyclobenzaprine oral tablets are dosed and given.
| Baclofen | Cyclobenzaprine | |
|---|---|---|
| Tablet strengths | 5 mg 10 mg 20 mg |
5 mg 7.5 mg 10 mg |
| Typical starting dose | 5 mg by mouth 3 times daily | 5 mg by mouth 3 times daily |
| Usual maximum daily dose | 20 mg by mouth 4 times daily | 10 mg by mouth 3 times daily |
| Duration of Use | 1-2 months, or until you and your healthcare provider decide to slowly stop the medication | 2-3 weeks |
| Kidney or liver function affects dosing | Yes, kidney | Yes, liver |
As a reminder, baclofen is also given as an injection into the back. It’s also available as an oral (by mouth) liquid. Cyclobenzaprine is also available as an oral capsule. If you have any questions about how these other dosage forms are used, talk with your pharmacist or healthcare provider.
How effective are baclofen and cyclobenzaprine for treating muscle spasms?
For muscle spasticity conditions — especially spinal injuries — experts consider baclofen as a possible first-choice option. Clinical trials showed that baclofen improved muscle tone in up to 72% of study participants.
For muscle spasms caused by muscle and bone issues, cyclobenzaprine is considered moderately effective. Studies have suggested that people taking cyclobenzaprine are 5 times more likely than placebo (a pill with no medication in it) to experience improvement in pain-related muscle symptoms.
What are the known side effects of baclofen and cyclobenzaprine?
Like all medications, both baclofen and cyclobenzaprine have a number of side effects. Some are common to both medications, and some are more unique to just one. Side effects can also vary by dose and dosage form (pill, injection, etc).
The following are some common side effects for common doses of baclofen and cyclobenzaprine:
| Side effect | Baclofen | Cyclobenzaprine |
|---|---|---|
| Drowsiness | 10-63% | 29% |
| Dry mouth | Rare | 21% |
| Dizziness | 5-15% | 1-3% |
| Weakness | 5-15% | Less than 1% |
| Headache | 4-8% | 5% |
What are the serious side effects of baclofen?
A number of rare but serious side effects are also possible. If you experience serious side effects with baclofen, such as the ones below, get medical help right away.
Sudden discontinuation (withdrawal) symptoms
Abruptly stopping baclofen can cause severe withdrawal symptoms, which can include seizures, unusual behavior, and more.
If you would like to stop using baclofen, talk with your healthcare provider first. They can help you slowly stop the medication to prevent withdrawal side effects.
Withdrawal symptoms in newborn babies
If you’re taking baclofen throughout your pregnancy, your healthcare provider may want to slowly stop this medication before your delivery date to limit withdrawal side effects in your baby. This is because within hours to days after delivery, newborn babies can experience withdrawal symptoms, such as rigid muscles, tremors, and seizures.
Seizures
In people with epilepsy, baclofen can raise the odds of having seizures. Your healthcare provider may want to closely monitor your brain waves over time to keep your seizure risk in check.
What are the serious side effects of cyclobenzaprine?
For cyclobenzaprine, seek immediate medical attention if you have symptoms like serotonin syndrome, heart-related side effects, or other similar symptoms.
Serotonin syndrome
Serotonin syndrome is a rare but potentially life-threatening condition. Symptoms of serotonin syndrome may include confusion, sweating, seizures, and tremors. Risk of serotonin syndrome is higher when you take cyclobenzaprine with other medications that raise serotonin levels. Serotonin is a naturally-occurring chemical in the body.
Heart-related side effects
Cyclobenzaprine might raise your risk for heart-related side effects, including a fast heartbeat and abnormal heart rhythm.
What interactions do baclofen and cyclobenzaprine have?
In general, don’t take baclofen or cyclobenzaprine with alcohol, opioid medications, or benzodiazepines. These can worsen side effects of your medication, like drowsiness or sleepiness.
You should also avoid taking cyclobenzaprine within 14 days of taking a monoamine oxidase inhibitor (MAOI). Combining cyclobenzaprine and MAOIs drastically raises your risk of serotonin syndrome. Examples of MAOIs include linezolid (Zyvox) and selegiline (Emsam).
Additionally, when taking cyclobenzaprine, use caution with tramadol (Ultram). Combining these two medications can worsen your seizure risk.
This is not a complete list of drug interactions for baclofen and cyclobenzaprine. For more detailed information about medication interactions for each muscle relaxant, talk with your pharmacist or healthcare provider.