Tizanidine was approved for medical use in the United States in 1996.[5] It is available as ageneric medication.[3] In 2023, it was the 81st most commonly prescribed medication in the United States, with more than 8million prescriptions.[7][8]
Side effects include dizziness, drowsiness, weakness, nervousness, confusion,hallucinations, strange dreams, 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]
Symptoms ofoverdose in 45 cases reported to a poison control center included: lethargy, bradycardia, hypotension, agitation, confusion, vomiting and coma.[10]
Tizanidine is anα2 receptor agonist closely related toclonidine. It has approximately one-tenth to one-fifteenth of the blood pressure-lowering effect of clonidine. The relation between the α2 receptor agonism and the spasmolytic action is still not fully understood.[2]
Tizanidine is available as a tablet or capsule. Capsules may be opened and sprinkled on food. However, this may change the absorption of the medication compared to taking the capsule whole.[16] It has avolume of distribution of 2.4 L/kg following intravenous administration.[1]
Tizanidine is a derivative of2,1,3-benzothiadiazole and its first published synthesis was reported in a patent.[17] The 5-chloro-2,1,3-benzothiadiazol-4-amine intermediate was a known compound, produced in three steps from 4-chlorophenylenediamine as shown.[18] Treatment with two equivalents ofthionyl chloride inpyridine formed theheterocycle, which wasnitrated withsodium nitrate insulfuric acid andreduced using iron and acetic acid.
^abKatzung BG (30 November 2017).Basic & clinical pharmacology (14th ed.). New York: McGraw Hill Education. p. 487.ISBN9781259641152.OCLC1015240036.
^abBritish national formulary: BNF 76 (76 ed.). Pharmaceutical Press. 2018. p. 1094.ISBN9780857113382.
^abKamen L, Henney HR, Runyan JD (February 2008). "A practical overview of tizanidine use for spasticity secondary to multiple sclerosis, stroke, and spinal cord injury".Current Medical Research and Opinion.24 (2):425–439.doi:10.1185/030079908X261113.PMID18167175.S2CID73086671.
^Spiller HA, Bosse GM, Adamson LA (January 2004). "Retrospective review of Tizanidine (Zanaflex) overdose".Journal of Toxicology. Clinical Toxicology.42 (5):593–596.doi:10.1081/CLT-200026978.PMID15462150.S2CID38946270.
^abcBlaxall HS, Murphy TJ, Baker JC, Ray C, Bylund DB (October 1991). "Characterization of the alpha-2C adrenergic receptor subtype in the opossum kidney and in the OK cell line".The Journal of Pharmacology and Experimental Therapeutics.259 (1):323–329.doi:10.1016/S0022-3565(25)20309-3.PMID1656026.
^abUS patent 3843668, Neumann P, "Certain 4-substituted amino-2,1,3-benzothiadiozoles", published 22 October 1974, assigned to Sandoz AG
^Pesin VG, Sergeev VA (1969). "Research on 2,1,3-thia- and selenadiazole".Chemistry of Heterocyclic Compounds.3 (5):662–666.doi:10.1007/BF00468340.S2CID98830770.
