People with stiff or tight muscles may be prescribed tizanidine or Flexeril to help ease these mild-to-painful conditions. Spinal injuries and neurological disorders such as cerebral palsy and multiple sclerosis can bring on muscle spasticity, limiting normal muscle movement. 

During spasticity, “the muscles remain contracted and resist being stretched, thus affecting movement, speech and gait,” the American Association of Neurological Surgeons explains

Tizanidine and Flexeril are both muscle relaxers that can be used with a physical therapy program. If your doctor has presented these options to you, you may be considering which one is right for you and wondering how they compare. Read on to find out what each drug does so that you are informed when you speak with your doctor about the best medication to take.

What Is Tizanidine?

Tizanidine is a short-acting muscle relaxer sold in the United States. It is more widely recognized by its trade name Zanaflex, and it was first approved for muscle spasm treatment in 1996. Only a medical professional can prescribe this medication, which acts on the central nervous system and treats multiple sclerosis and certain spinal injuries. It comes in the form of a capsule or tablet. Side effects include dizziness, drowsiness, and muscle weakness. 

What Is Flexeril?


Flexeril is a muscle relaxant that can be prescribed as part of a treatment for muscle spasticity that includes physical therapy and rest. The brand name Flexeril has been discontinued in the U.S., but its generic form, cyclobenzaprine hydrochloride, is still sold in the country. Generic forms may be sold under Amrix, an extended-release capsule, and Fexmid, an immediate-release capsule. The medication also works on the central nervous system and blocks nerve signals to the brain, which helps to relax muscles and prevent spasms. This also helps users avoid severe pain during therapy. Flexeril is recommended for short-term use. Common side effects include dizziness, drowsiness, dry mouth, and muscle weakness. Users are urged to follow all directions on their prescription label and know that their doctor could occasionally change their dose.

Which Muscle Relaxant Is Stronger?

Based on each medication’s dosage schedules, tizanidine could be slightly stronger over time. Treatment on either medicine starts with a small dose that is gradually increased under a doctor or pharmacist’s direction. 

According to, tizanidine treatment usually starts with an initial dose of 2 mg (milligrams) that is taken every six to eight hours three times a day. The dosage may then be increased to 2 to 4 mg every one to four days. A maximum daily dose is 36 mg. How long therapy runs depends on the person’s condition. 

Cyclobenzaprine treatment with the immediate-release medication usually starts with an initial dose of 5 mg that is taken by mouth three times a day. The dosage may then be increased to 10 mg orally three times a day based on how the person responds. Therapy usually lasts up to three weeks. Treatment with the extended-release form starts with an initial dose of 15 mg once a day that may be increased to 30 mg based on the person’s response. Therapy also lasts up to three weeks.

How Are They Different?

Tizanidine and Flexeril (cyclobenzaprine) have their differences. They differ by the dosage prescribed and treatment length, and they also have different half-lives, the time it takes for the drug to reduce by one-half, or 50 percent, in the bloodstream. Zanaflex’s half-life is roughly 2.5 hours, while Flexeril’s half-life is 18 hours. 

Also, cyclobenzaprine is chemically similar to the tricyclic class of antidepressants, according to MedicineNet. This means it shouldn’t be taken with or within two weeks of any monoamine oxidase inhibitor (MAOI), a medication that treats depression. 

Zanaflex has been approved to treat muscle spasticity linked to multiple sclerosis and spinal cord injuries. Flexeril, or cyclobenzaprine, is used to treat skeletal muscle pain and spasms. Cyclobenzaprine also comes in an extended-release version. Your doctor can help you figure out which drug is best for your situation.

Tizanidine and cyclobenzaprine use in high doses can cause liver damage. However, a study of long-term tizanidine use concluded that this medicine is relatively safe, effective, and well-tolerated. However, no research suggests that long-term cyclobenzaprine use is safe or effective.

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