API: Tizanidine Hydrochloride

What Is Tizanidine Hydrochloride and How Does It Work?

Tizanidine hydrochloride is short-acting muscle relaxant that essentially works by blocking nerve impulses to the brain and relaxing muscle tone. Although the exact mechanism of action for the drug is not entirely known, tizanidine hydrochloride is a centrally acting α2-adrenergic agonist that primarily affects spinal polysynaptic reflexes.1 The drug increases pre-synaptic inhibition of motor neurons by impairing the release of amino acids that help motor neurons and the central nervous system communicate, and by inhibiting certain pathways in the spinal cord.2 Tizanidine hydrochloride is primarily used to manage and treat skeletal muscle spasms due to multiple sclerosis or spinal cord injury.

  • Spasticity: This drug is used to treat muscle spasms due to conditions such an injury to the spinal cord, multiple sclerosis, brain trauma, or stroke. It is short-acting and should be used for daily activities that require immediate relief.

Side Effects and Drug Interactions

Common side effects in patients taking tizanidine hydrochloride include3:

  • Drowsiness
  • Dizziness
  • Anxiety
  • Numbness
  • Stomach ache or fever
  • Diarrhea or constipation
  • Dry mouth
  • Vomiting
  • Muscle weakness or increased muscle tone and spasms
  • Back pain
  • Sweating
  • Skin rash

Patients who suffer from severity of these common side effects should contact their pharmacist or physician right away. Patients who experience an allergic reaction (hives, trouble breathing, swelling of the face, lips, tongue, or throat) or light-headedness, fainting, a decreased heart rate, hallucinations, confusion or other unusual thoughts and behavior, loss of appetite, dark urine, clay-colored stools, jaundice, or burning when urinating should contact their physician immediately.

Patients who are allergic to tizanidine hydrochloride should not take this drug. This drug is contraindicated in patients who are taking strong CYP1A2 inhibitors, such as fluvoxamine or ciprofloxacin. Patients who have or who have had hepatic or renal impairment should inform their physician before starting this drug. Tizanidine has been shown to decrease fertility in both men and women. The drug is not advised for pregnant women; studies have not been performed in patients who are breastfeeding or in children. The drug has some effect in lowering blood pressure; patients on medications for blood pressure should seek an alternative drug.

Latest News and Research

Tizanidine hydrochloride is currently available as a tablet or gel cap, and in injection form. Research is ongoing with respect to other routes and formulations for easier delivery of more bioavailable drug. A recent investigation on the use of nightly sublingual tizanidine hydrochloride versus oral tablets in multiple sclerosis patients experiencing spasms showed that the sublingual therapy was effective without increasing next-day somnolence that oral tablets cause.4 Since daytime drowsiness caused by the oral tablets is a primary cause of patient dissatisfaction and noncompliance, this new formulation may provide more effective treatment.

Buccal delivery of the drug is another area of significant study. This type of drug delivery is particularly viable for patients who can’t take oral pills and is typically done through adhesive mucosal dosage forms in the form of tablets, gels, or patches. One type of formulation under study is bilayered buccal tablets of the drug using mucoadhesive polymers against an impermeable backing layer.5

Another group is developing buccal patches, which must be flexible, elastic, and strong for use within the mouth, but which must also have enough mucoadhesion to stay in the mouth for the time needed.6 A monolayered buccal patch using the polymer Eudragit® RL 100 and chitosan seems to effective at delivering tizanidine hydrochloride through gradual release.

Tizanidine hydrochloride is also under study for use in a variety of indications, such as chronic back pain.7 In a study of 60 patients with chronic low-back pain, eperisone and tizanidine in combination treatment with tramadol was shown to be effective at reducing pain. Tizanidine hydrochloride may also be a safe and effective treatment of children who have dysfunctional voiding due to dysfunction of the pelvic floor/skeletal sphincter.8 The theory that tizanidine hydrochloride may be an effective treatment for alcohol withdrawal syndrome is also under study.9

Buying Guide

Many compound pharmacists find that Baclofen is a safer alternative for treating muscle spasms. Please find more information about our Bulk APIs here.

Show 9 footnotes

  1. “TIZANIDINE HYDROCHLORIDE – tizanidine hydrochloride tablet,” September 2009, http://dailymed.nlm.nih.gov/dailymed/archives/fdaDrugInfo.cfm?archiveid=20674
  2. “Tizanidine: neuropharmacology and mechanism of action,” November 1994, http://www.ncbi.nlm.nih.gov/pubmed/7970012
  3. “Zanaflex,” April 24, 2015, http://www.rxlist.com/zanaflex-side-effects-drug-center.htm
  4. “Nightly Sublingual Tizanidine HCl in Multiple Sclerosis: Clinical Efficacy and Safety,” May 2010, http://journals.lww.com/clinicalneuropharm/Abstract/2010/05000/Nightly_Sublingual_Tizanidine_HCl_in_Multiple.8.aspx
  5. “Mucoadhesive Bilayered Buccal Tablets of Tizanidine Hydrochloride,” July-Sept 2010, http://sphinxsai.com/july-sept_2010_vol2.3/pharmtech/pharmtechvol2.3july-sept210/PT=34%20_1861-1869_.pdf
  6. “Formulation and evaluation of a bioadhesive patch for buccal delivery of tizanidine,” June 2012, http://www.sciencedirect.com/science/article/pii/S2211383512000287
  7. “Eperisone versus tizanidine for treatment of chronic low back pain,” 2012, http://europepmc.org/abstract/med/22653094
  8. “Doxazosin Versus Tizanidine for Treatment of Dysfunctional Voiding in Children: A Prospective Randomized Open-labeled Trial,” February 2012, http://www.sciencedirect.com/science/article/pii/S0090429511025799
  9. “Tizanidine for alcohol withdrawal treatment,” October 2011, http://www.sciencedirect.com/science/article/pii/S0306987711002866