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Tizanidine ball-and-stick.png
Clinical data
Pronunciation/tˈzænɪdn/ tye-ZAN-i-deen
Trade namesZanaflex, Sirdalud, and others
  • C
Routes of
Oral administration (tablets, capsules)
ATC code
Legal status
Legal status
Pharmacokinetic data
Protein binding~30%
MetabolismLiver (CYP1A2, 95%)
Elimination half-life2.54 hours (tizanidine), 20–40 hours (inactive metabolites)[1]
ExcretionUrine (60%), feces (20%)
CAS Number
PubChem CID
ECHA InfoCard100.125.400 Edit this at Wikidata
Chemical and physical data
Molar mass253.71 g·mol−1
3D model (JSmol)

Tizanidine (trade names Zanaflex, Sirdalud, and others) is a centrally acting α2 adrenergic agonist used as a muscle relaxant. 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 acute liver failure. 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 six months of treatment. As of 2015 the cost for a typical month of medication in the United States is US$100–200.[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 humans, resulted in a 33-fold increase in the tizanidine AUC (plasma drug concentration-time curve).[1] For this reason both fluvoxamine and tizanidine should not be taken at the same time. 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 central nervous system depressants. Alcohol should be avoided, particularly as it can upset the stomach. The CNS-depressant effects of tizanidine and alcohol are additive.[1] Caution with the following interactions[6][7][8]:

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

Side effects[edit]

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.[9]

See also[edit]


  1. ^ a b c d e "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". www.fibromyalgia-reviews.com. Retrieved 4 September 2017.
  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 978-1-284-05756-0.
  5. ^ "Tizanidine Uses, Dosage, Side Effects – Drugs.com". drugs.com. Retrieved 4 September 2017.
  6. ^ NHS Wales (2011). "Tizanidine (Zanaflex) Gwent Primary Care Prescribing Guidance" (PDF). Aneurin Bevan University Health Board.
  7. ^ "Tizanidine package leaflet: Information for the user" (PDF). Medicines and Healthcare products Regulatory Agency (UK). 2016.
  8. ^ "Zanaflex (tizanidine hydrochloride) dose, indications, adverse effects, interactions... from PDR.net". www.pdr.net. Retrieved 2018-09-16.
  9. ^ pmhdev. "Page not available". PubMed Health. Archived from the original on 11 November 2012. Retrieved 4 September 2017.