What is tizanidine (Zanaflex) used for?

Tizanidine: Uses and Clinical Applications

Tizanidine is primarily used for the management of spasticity associated with conditions such as multiple sclerosis, spinal cord injury, and cerebral disorders, and has emerging applications in pain management including acute low back pain. 1

Primary Indications

Tizanidine (Zanaflex) is an α2-adrenergic receptor agonist with the following FDA-approved and evidence-supported uses:

Spasticity Management

• FDA-approved for the management of spasticity 1
• Particularly effective for:
  • Multiple sclerosis 2
  • Spinal cord injury 3
  • Cerebral disorders 4

Low Back Pain

• Well-studied and effective for acute low back pain 5
• Shown to be efficacious in 8 clinical trials for acute low back pain 5
• Considered an option for short-term relief of acute low back pain 5

Mechanism of Action

Tizanidine works through specific mechanisms:

• Acts as an agonist at α2-adrenergic receptor sites 1
• Reduces spasticity by increasing presynaptic inhibition of motor neurons 1
• Structurally related to clonidine but with 1/10 to 1/50 of its blood pressure-lowering effects 1
• Classified as a centrally acting spasmolytic agent 5

Clinical Considerations

Dosing

• Requires individualized dosage titration over 2-4 weeks 4
• Typical dosage range: 2-36 mg/day 4
• Short-acting with peak effects occurring within 2 hours of administration 1, 4
• Should be reserved for times when relief of spasticity is most important due to short duration of effect 1

Efficacy

• Reduces mean muscle tone scores by 21-37% (vs 4-9% with placebo) 4
• Improvement in muscle tone occurs in 60-82% of patients 4
• Comparable efficacy to baclofen for spasticity management 4
• Also reduces spasm frequency and clonus 4, 6

Advantages

• Does not significantly reduce muscle strength (unlike some other muscle relaxants) 4
• Less subjective muscle weakness compared to baclofen or diazepam 4
• Better tolerated than many other muscle relaxants 4
• May have perioperative benefits including improved postoperative pain control and decreased opioid consumption 5

Adverse Effects and Precautions

Common Side Effects

• Sedation/drowsiness (dose-dependent) 5, 4
• Dry mouth (xerostomia) 4, 3
• Dizziness, ataxia, lethargy 5
• Fatigue 3

Important Precautions

• Should be avoided in patients with hepatic or renal dysfunction 5
• Use with caution in elderly patients due to sedative and hypotensive effects 5
• Risk of withdrawal symptoms (rebound tachycardia, hypertension, hypertonia) with abrupt discontinuation 5
• Significant drug interactions with CYP1A2 inhibitors (contraindicated with ciprofloxacin and fluvoxamine) 5

Perioperative Considerations

• Can be continued preoperatively including the day of surgery 5
• If discontinuation is necessary in long-term users, should be tapered slowly 5

Clinical Applications Beyond Spasticity

Emerging evidence supports tizanidine's use in:

• Myofascial pain 7
• Chronic neck pain 7
• Lower back pain (both acute and chronic) 5, 7
• Trigeminal neuralgia 7

Tizanidine represents an important therapeutic option for spasticity management with a favorable side effect profile compared to other muscle relaxants, particularly regarding preservation of muscle strength. When used for acute low back pain, it should be prescribed for short-term relief with careful monitoring for sedation and other adverse effects.