Tizanidine
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| Pronunciation | /taɪˈzænɪdiːn/ tye-ZAN-i-deen |
| Trade names | Zanaflex, Sirdalud, and others |
| Other names | 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 |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a601121 |
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| Routes of administration | By mouth |
| Drug class | α2-adrenergic receptor agonist |
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| Pharmacokinetic data | |
| Bioavailability | ~40% |
| Protein binding | ~30% |
| Metabolism | Liver (CYP1A2, 95%) |
| Elimination half-life | 2.54 hours (tizanidine), 20–40 hours (inactive metabolites) |
| Excretion | Urine (60%), feces (20%) |
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| ECHA InfoCard | 100.125.400 |
| Chemical and physical data | |
| Formula | C9H8ClN5S |
| Molar mass | 253.71 g·mol−1 |
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Tizanidine, sold under the brand name Zanaflex among others, is an alpha-2 (α2) adrenergic receptor agonist, similar to clonidine, that is used to treat muscle spasticity due to spinal cord injury, multiple sclerosis, and spastic cerebral palsy. Effectiveness appears similar to baclofen or diazepam. It is taken by mouth.
Common side effects of tizanidine include dry mouth, sleepiness, weakness, and dizziness. Serious side effects may include low blood pressure, liver problems, psychosis, and QT prolongation. It is unclear if use in pregnancy and breastfeeding is safe. It is an α2-adrenergic agonist, but how it works is not entirely clear.
Tizanidine was approved for medical use in the United States in 1996. It is available as a generic medication. In 2022, it was the 94th most commonly prescribed medication in the United States, with more than 6 million prescriptions.