|Trade names||Lorzone, Paraflex ,Muscol|
|Elimination half-life||1.1 hr Duration of action 3-4 hrs.|
|CompTox Dashboard (EPA)|
|Chemical and physical data|
|Molar mass||169.56 g·mol−1|
|3D model (JSmol)|
Chlorzoxazone (INN) is a centrally acting muscle relaxant used to treat muscle spasm and the resulting pain or discomfort. It can also be administered for acute pain in general and for tension headache (muscle contraction headache). It acts on the spinal cord by depressing reflexes. It is sold under the brand names Lorzone, Paraflex and Muscol and in combination form as Parafon Forte, a combination of chlorzoxazone and acetaminophen (paracetamol). Possible side effects include dizziness, lightheadedness, malaise, nausea, vomiting, and liver dysfunction. Used with acetaminophen it has added risk of hepatotoxicity,[medical citation needed].
Like metaxalone, its mechanism of action is still in question. It is believed that metaxalone works by altering serotonin levels and acting as a mild MAO inhibitor.[medical citation needed] The mechanism of action of chlorzoaxazone is thought[by whom?] to act on Gaba-A & B receptors and voltage-gated calcium channels to a degree.[medical citation needed] General central nervous system depression is the only currently accepted aspect to its medical benefits.[medical citation needed] Elucidation of the exact mechanism of action is ongoing but there is limited study due to the existence of more effective, safe muscle relaxants (ex. diazepam, cyclobenzaprine, tizanidine), greatly limiting the potential benefit of identifying novel compounds which share chlorzoxazone's mechanism of action.