Flexeril vs. Zanaflex

See how Flexeril and Zanaflex compare on approved uses, dosing, side effects, and cost.

Key Takeaways

  • Flexeril treats short-term muscle spasm from injuries and isn't meant for use beyond 2 to 3 weeks, while Zanaflex is approved for ongoing spasticity from conditions like multiple sclerosis or spinal cord injury.

  • Both drugs commonly cause drowsiness and dry mouth, but Zanaflex also requires periodic liver testing and carries risks of low blood pressure and slowed heart rate.

  • Flexeril typically costs less each month than Zanaflex, though both are available as generics.

Flexeril vs. Zanaflex Drug Summary

Flexeril

Flexeril (cyclobenzaprine) is a tricyclic-related skeletal muscle relaxant used short-term for spasms from acute muscle injuries. It's taken as an oral tablet, usually three times a day, along with rest and physical therapy. Only the generic form is sold in the U.S. today.

Zanaflex

Zanaflex (tizanidine) is a central alpha-2 agonist muscle relaxant used to manage spasticity in adults with conditions like MS. It's taken as an oral tablet or capsule, increased gradually across several doses each day. Its effects wear off quickly, so doses are often timed to specific activities.

Flexeril vs. Zanaflex Side Effects

Flexeril

Most common
dry mouth (up to 27%)
dizziness (up to 11%)
drowsiness (up to 39%)
fatigue (up to 6%)

Zanaflex

Most common
dry mouth (up to 49%)
dizziness (up to 16%)
somnolence/sedation (up to 48%)
weakness (up to 30%)

Flexeril vs. Zanaflex Dosage

Flexeril

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 5 mg three times daily At the start
Maximum dose 10 mg three times daily If needed
Dose changes 1 increase As tolerated

Zanaflex

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 2 mg every 6-8 hours At the start
Maximum dose 36 mg/day maximum If needed
Dose changes 4 increases As tolerated

Flexeril vs. Zanaflex Indications

Flexeril

Flexeril is FDA-approved as a short-term add-on to rest and physical therapy for muscle spasm from acute musculoskeletal injuries, like a back strain. It is not approved for spasticity caused by conditions such as cerebral palsy or spinal cord injury. Some clinicians use it off-label for fibromyalgia pain and sleep symptoms.

  • Adjunct to rest and physical therapy for acute spasm

  • Short-term use only, typically 2 to 3 weeks

  • Off-label: fibromyalgia pain and sleep symptoms

  • Not effective for spasticity from CNS disease

Zanaflex

Zanaflex is FDA-approved to manage spasticity in adults, a condition often caused by multiple sclerosis, spinal cord injury, or stroke. It works directly on the central nervous system to reduce muscle tightness rather than treating short-term spasm. It is not approved for use in children.

  • Management of spasticity from MS or spinal injury

  • Used for ongoing, chronic muscle tightness

  • Dosing often timed around specific daily activities

  • Not approved for pediatric patients

Flexeril vs. Zanaflex Pros and Cons

Flexeril

Flexeril works well for short-term, acute muscle spasm and has decades of clinical use behind it. It is not intended for long-term treatment and carries several cardiac-related contraindications. Coverage is usually straightforward because inexpensive generics have long been available.

Pros

  • Lower typical monthly cost than Zanaflex

  • No liver enzyme monitoring required

  • Long track record of clinical use since 1977

  • Three tablet strengths for flexible dosing

Cons

  • Not recommended for use beyond 2 to 3 weeks

  • Ineffective for spasticity from CNS conditions like MS

  • Contraindicated with several heart conditions and MAOIs

  • Drowsiness affects up to 39% of patients

Zanaflex

Zanaflex is approved for longer-term spasticity management and offers dosing flexibility timed to specific activities. Its side effect profile includes hypotension, sedation, and a need for liver monitoring at higher doses. Cost is typically higher than short-term muscle relaxants like Flexeril.

Pros

  • Approved for long-term spasticity, not just short-term spasm

  • Effective for spasticity from MS or spinal cord injury

  • Short duration lets dosing match specific activities

  • Available generically, reducing cost versus brand

Cons

  • Higher typical monthly cost than Flexeril

  • Requires liver enzyme monitoring at baseline and peak dose

  • Can cause hypotension, bradycardia, and syncope

  • Risk of rebound hypertension if stopped abruptly

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