Tizanidine

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 2020, it was the 84th most commonly prescribed medication in the United States, with more than 8 million prescriptions. Tizanidine has been found to be as effective as other antispasmodic drugs and is more tolerable than baclofen and diazepam. 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. Symptoms of overdose in 45 cases reported to a poison control center included: lethargy, bradycardia, hypotension, agitation,confusion, vomiting and coma. Tizanidine has drug abuse potential. It has been recognized to cause dependence and addiction. In the US it is not regulated under the Controlled Substances Act, however. 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).