Clinical data
Pronunciation tye-ZAN-i-deen
Trade names Zanaflex, Sirdalud
AHFS/Drugs.com Monograph
MedlinePlus a601121
  • C
Routes of
By mouth (tablets, capsules)
ATC code M03BX02 (WHO)
Legal status
Legal status
Pharmacokinetic data
Bioavailability ~40%[1]
Protein binding ~30%
Metabolism Liver (CYP1A2, 95%)
Biological half-life 2.54 hours (tizanidine), 20–40 hours (inactive metabolites)[1]
Excretion Urine (60%), feces (20%)
Synonyms 4-Chloro-N-(4,5-dihydro-1H-imidazol-2-yl)-8-thia-7,9-diazabicyclo[4.3.0]nona-2,4,6,9-tetraen-5-amine
CAS Number 51322-75-9 YesY
PubChem (CID) 5487
DrugBank DB00697 YesY
ChemSpider 5287 YesY
KEGG D08611 YesY
ECHA InfoCard 100.125.400
Chemical and physical data
Formula C9H8ClN5S
Molar mass 253.712 g/mol
3D model (Jmol) Interactive image

Tizanidine (trade names Zanaflex (Acorda Therapeutics), Sirdalud (Novartis), Relentus (Beximco Pharma)) is a drug that is used as a muscle relaxant. It is a centrally acting α2 adrenergic agonist. It is used to treat the spasms, cramping, and tightness of muscles caused by medical problems such as multiple sclerosis, ALS, spastic diplegia, back pain, or certain other injuries to the spine or central nervous system. It is also prescribed off-label for migraine headaches, as a sleep aid, and as an anticonvulsant. It is also prescribed for some symptoms of fibromyalgia.[2]

Tizanidine has been found to be as effective as other antispasmodic drugs and is more tolerable than baclofen and diazepam.[3] Tizanidine can be very strong even at the 2 mg dose and may cause hypotension, so caution is advised when it is used in patients who have a history of orthostatic hypotension, or when switching from gel cap to tablet form and vice versa.

Tizanidine can occasionally cause liver damage, generally the hepatocellular type. Clinical trials show that up to 5% of patients treated with tizanidine had elevated liver function test values, though symptoms disappeared upon withdrawal of the drug. Care should be used when first beginning treatment with tizanidine with regular liver tests for the first 6 months of treatment. As of 2015 the cost for a typical month of medication in the United States is 100 to 200 USD.[4]


Concomitant use of tizanidine and moderate or potent CYP1A2 inhibitors (such as zileuton, certain antiarrhythmics (amiodarone, mexiletine, propafenone, verapamil), cimetidine, famotidine, aciclovir, ticlopidine and oral contraceptives) is contraindicated. Concomitant use of tizanidine with fluvoxamine, a potent CYP1A2 inhibitor in man, resulted in a 33-fold increase in the tizanidine AUC (plasma drug concentration-time curve).[1] Fluoroquinolone antibiotics such as moxifloxacin, levofloxacin, and ciprofloxacin should also be avoided due to an increased serum concentration of tizanidine when administered concomitantly.[5] Tizanidine has the potential to interact with other CNS depressants. Alcohol should be avoided, particularly as it can upset the stomach. The CNS-depressant effects of tizanidine and alcohol are additive.[1]

It has a volume of distribution of 2.4 L/kg following intravenous administration.[1]

Side effects

Side effects include dizziness, drowsiness, weakness, nervousness, hallucinations, depression, vomiting, dry mouth, constipation, diarrhea, stomach pain, heartburn, increased muscle spasms, back pain, rash, sweating, and a tingling sensation in the arms, legs, hands, and feet.[6]

See also


  1. 1 2 3 4 5 "Zanaflex (tizanidine hydrochloride) Capsules and Tablets for Oral Use. Full Prescribing Information" (PDF). Acorda Therapeutics Inc. Ardsley, NY 10502. Retrieved 1 September 2016.
  2. Zanaflex for Fibromyalgia
  3. Kamen, L.; Henney, HR.; Runyan, JD. (Feb 2008). "A practical overview of tizanidine use for spasticity secondary to multiple sclerosis, stroke, and spinal cord injury.". Curr Med Res Opin. 24 (2): 425–39. doi:10.1185/030079908X261113. PMID 18167175.
  4. Hamilton, Richart (2015). Tarascon Pocket Pharmacopoeia 2015 Deluxe Lab-Coat Edition. Jones & Bartlett Learning. p. 3. ISBN 9781284057560.
  5. Tizanidine Uses, Dosage, Side Effects - Drugs.com
  6. Tizanidine - PubMed Health
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